page 97 note * The Geologist, vol. i. p. 409. 1858 Google Scholar. This paper has been translated into French by my friend Professor L. de Koninck, and will be published in the Transactions of the Royal Society of Liège, for 1859.

page 98 note * In order to avoid further repetitions, I may mention once more that the muscles the function of which is to open or separate the valves have recently been termed divaricators and accessory divaricators by Mr. Hancock; and those the function of which is to act in the closing of the valves have been termed anterior and posterior occlusors by the same distinguished zoologist. The divaricators are those usually termed “cardinal muscles” (“adductor brevis” of Owen; “muscles diducteurs” of Gratiolet); while the accessory divaricators are better known by the name of “accessory cardinals” or “cardinalis” of Owen.

The occlusor is the “adductor” of the generality of authors; the anterior occlusor being the “adductor longue anticus” of Owen; the posterior occlusor, the “adductor longus posticus” of the same distinguished anatomist.

The pedicle-muscles have been termed adjustors by Mr. Hancock, under the belief that they move the shell upon its peduncle, and adjust it; while the “capsularis” of Owen, is Hancock's peduncular muscle.

page 100 note * In the last page of the German edition of my “General Introduction” (Vienna, 1856), Professor Suess has appended a list of no leas than 160 generic names, under which the known species of Brachiopoda had been located up to the year 1856 ! And since that period, several others have been proposed by Messrs. Hall, Suess, and Billings. In the French edition of the same work, I provisionally admitted 24 genera and 22 sub-genera, making a total of 46; but of these, a few were mentioned with doubt; and, although I believe we are working in the right path, much care must be exercised not to exaggerate the number of genera and sub-genera, and thus to be causing confusion where simplicity should prevail.

page 101 note * Family names are derived from those in the typical genera; and, as in the present instance Strophomena and Productus were established first, it behoves us to admit them in preference to others subsequently introduced. Naturalists have not hitherto agreed as to what should constitute a genus or sub-genus; and as some even entirely object to the term “sub-genus,” I have not made any such distinctions in the table here given; but I have endeavoured to arrange the names according to their more probable affinities. When treating of the Strophomenidæ, we will endeavour carefully to compare the different “genera” or “sub-genera” with each other; as the differential characters do not appear to me to have been in all cases satisfactorily established.

page 102 note * It is likewise certain that some examples of Orthis resupinata and O. Kerserlingiana were furnished with small scattered spines. Probably such spines have escaped observation, not merely from their being of a very delicate nature, and consequently liable to abrasion and injury before being buried up in the ancient mud, but oftener, possibly, through the hardness of the limestone-matrix which adheres to the outer surface, causing the latter usually to flake off in breaking out the specimens, and which remains in the mould undetached from the embedded spines. For the opposite reason, probably, it is that specimens from shales are generally more perfect than those from limestones.

page 103 note * In the tenth volume of the Quarterly Journal of the Geological Society (p. 202, pl. VIII. 1853). I described and figured as Chonetes comoides several remarkable exteriors and interiors, which, I believe, along with Messrs. Salter, Woodward, and King, to be referable to a single species (Pl. IV. fig. 7). The sharply defined and well-developed area in each valve, the fissure in the ventral one, and the produced cardinal process in the other, as well as the strongly articulated hinge, have up to the present time been considered characters peculiar to Chonetes, and not to Producta, especially since all well-authenticated species and specimens (hitherto examined) of the last-named genus have proved to be edentulous. Small pits, observable at intervals along the cardinal edge in several examples which I then or have subsequently examined, seemed also to denote the existence of small cardinal spines, similar to those observable in certain species of Chonetes; nor do the muscular impressions in the interior of the ventral valve (unfortunately only one specimen is at present known) militate against such a conclusion. If, therefore, the shells in question belong to Producta, and not to Chonetes (as Professor de Koninck appears disposed to believe), the genus or sub-genus Chonetes would become superfluous, and our notions regarding Producta require material alteration, since the genus would be made to contain both edentulous as well as strongly articulated species. Such a supposition would demand much further examination and confirmation before being admitted as a definitely settled fact. At the time the paper above referred to was communicated, Mr. D. Sharpe announced that in his opinion fig. 1 alone belonged to Chonetes comoides, and that fig. 2, &c. were referable to another, although closely allied, species. Since that period Professor de Koninck has referred them to Producta hemispherica, Sow. There again I must be allowed to observe that none of Sowerby's original specimens of the last-named species show any area, nor apparently any articulated hinge; they bear, however, so exact a resemblance to a true Producta that it would be necessary to examine a larger number of specimens before I possibly could conscientiously admit the identification to be strictly correct I am happy, however, to know that my distinguished friend, who has devoted so much time to the study of the species of which this family is composed, intends shortly to issue a supplement to his great work, in which he will fully express his views regarding the subject of the present note.

page 104 note * A very remarkable specimen of Producta semireticulata, which at one time formed part of Mr. Charlesworth's collection, illustrating this feature, has been recently added to the British Museum. This also presents a small peeudo-deltidium.

page 106 note * In the plates accompanying this article the same letters are used for the corresponding parts as are inserted in the woodcuts.

page 108 note * Mr. Hancock informs me that the occlusors are undoubtedly formed of two elements, the anterior and posterior, and that we should not therefore be surprised to find indications of the two component parts in the ventral as well as in the dorsal valve. In Lingula the anterior and posterior occlusors are distinct, having four points of attachment in each valve.

page 108 note † Prof. King has figured in his monograph of English Permian Fossils (Pl. XIX. fig. 2) what he terms vascular markings in connexion with these large muscular scars, and which seem to form part of the impression. Mr. Hancock appears disposed to consider the whole to be the scar of one muscle, and that there is nothing extraordinary in this, as it frequently happens that the same thing may be seen in the Unionidæ and other Conchifera.

page 108 note ‡ Although the case in question may not apply directly to Producta, it will be as well to mention that Mr. Hancock has found in Lingula three pairs of adjustors apparently for the purpose of keeping the valves opposed to each other and of holding them adjusted. In this respect, they appear well calculated to compensate for the entire absence of hinge or teeth. He explains this in the following words: —“The external or ventral pair having their anterior extremities attached to the ventral valve—which, as it is fixed to the peduncle, is that from which all muscles act—and their posterior ends to the dorsal, it is evident that they will prevent the latter from being forced backwards; while the posterior adjustors having their terminations united to the ventral or fixed valve, and their anterior portion to the dorsal, they will act in the contrary direction, and guard against the pressure forward; they will also at the same time prevent any lateral displacement of the valves, as their diagonal position will enable them to act transversely, as well as longitudinally. The external and central adjustors will, on account of their oblique arrangement, exert a similar double influence in front” See Mr. Hancock's admirable memoir on the anatomy of the Brachiopoda, published in the “Transactions of the Royal Society” for 1858.

Mr. Howse remarks, in his paper, published in the Annals of Natural History (1857), that, when the cardinal process of Producta is in situ, it fills nearly the whole of the umbonal cavity of the ventral valve, and may thus assist in keeping the valves in position. It is possible, however, that future researches by the aid of better preserved specimens, may enable us to discover some traces of adjustor muscles.

page 109 note * In his Memoir, Mr. Hancock has stated that the brachial appendages subserve at once the function of gills and of sustentation. To prove that they are aerating organs, “it is only necessary to refer to the manner in which the blood circles round the arms, and is carried to the cirri, but more particularly to its circulating through these latter organs, and to its return direct from them to the heart.”

page 111 note * In a letter I had the pleasure of receiving from Count Keyserling, it is stated, that, “if in the ventral valve of Producta gigantea, and some few others, we see the indication of obscure spiral depressions, this may be due to the unattached portion of the arms; but that we perceive no similar hollows in the same valve of the greater number of species;” but it should also be remembered that we cannot expect to find hollows in those forms in which the valve was too thin to admit of similar depressions.

page 111 note † The Geologist, Vol I., Pl. XII. figs. 33, 34.

page 112 note * In a letter I have recently received from Mr. Hancock, there is the following passage:— “The idea that the reniform impressions gave support to the arms does not appear inconsistent with the opinion expressed by you and others, namely, that a portion of each arm was arranged spirally, and occupied the hollows in the ventral valve. I am quite inclined to believe that these reniform callosities gave support to the first or basal portion of the arms. The arms may afterwards have become free, and have formed more or less incomplete spirals, and may have fitted into the subspiral cavities of the ventral valve in Producta gigantea, &c. In some other species no spirals may have been developed, and the extremities of the arms may have been disposed in some other manner. In Thecidium the terminal portions are variously arranged; and this may have been the case in the Productidæ. It is impossible not to be struck with the resemblance of the reniform impressions in fig. a of your Pl. IV., to the ridges supporting the arms of Thecidium in Pl. VI. fig. 42, of your General Introduction.”

Professor King explains his views regarding the origin of the reniform impressions in the following words, which I think it well to reproduce in this place, that the reader may have before him the reasons adduced by those who would connect the above-mentioned impressions with the vascular system, as well as of those who attribute them to the ridges supporting the arms:—

“Taking Leptæna analoga and Productus horridus, as examples illustrating the characterism of the vascular system of their respective families, it may be predicated of Strophomenidæ, that the primary pallial vessels are more or less confined to the medio-longitudinal region of the valves; and of Productidæ, that they strike off at the moment they issue from between the muscular scars, in a lateral direction, running for some distance nearly parallel to the cardinal line, then curving forward and round towards the centre, and finally returning to nearly their origin. Looking at the vein-like line bounding the reniform lobes of Productus horridus [see the woodcuts] and P. semireticulatus, I cannot but think that these structures are each due to a recurving vessel, rather than to an expanded and simply projecting vascular organ, as appears to be the case in Oriapus (Cramia).”

page 114 note * Those who may feel desirous for more ample information concerning the Productidæ, will do well to consult Prof. de Koninck's excellent “Monographie des Genres Productus et Chonetes, Liège, 1847;” also the second volume of the “Geology of Russia, in Europe and the Ural” (1845); Count Keyserling's “Petschoraland” (1846); King's “Monograph of the Permian Fossils of England” (1850); Sowerby's “Mineral Conchology;” Woodward's “ Manual of the Mollusca,” and various other works and papers by MM. de Verneuil, Geinitz. Kutorga, Martin, and Howse, as well as the three editions of my “General Introduction,” &c. In my “Monograph of British Permian Brachiopoda,” published in 1858, the subject has also been attentively re-examined; ana it may not here perhaps be considered out of place for me to remark, that during the careful preparation of that work, which occupied the greater portion of my time during one year and a half, I did my very utmost to be just and fair towards all concerned, allowing no bias or preference to interfere with my judgment; and although I may be mistaken with respect to certain scientific questions, I have not hitherto perceived any valid grounds for altering the conclusions therein expressed.