The present paper is a continuation of that published in the Geological Magazine, vol LXII, NO. IV, April, 1925 PP.145–80.

In the Geological Magazine for May appeared an article by Dr. R. H. Rastall entitled “On the Tectonics of the Southern Midlands”, which I feel it absolutely necessary to criticize and correct in so far as it deals with evidence derived from Northamptonshire and quotations from my own papers, the latter in parts verbally accurate and yet altogether misleading as used; and I trust Dr. Rastall will accept the following corrections and additions rather as a contribution than an adverse criticism merely to his theory of “the recurrence of activity along old-established fold-lines of an early date–5, and will be separately referred to.

Since Dr. J. M. Clarke's1 attempt in 1890 to subdivide the Acidaspidae (= Odontopleuridae) by means of the characters of the occipital ring and its spines, several other methods of classification of the members of this family have been proposed. Van Ingen,2 in 1901, adopted Clarke's names for the subgenera which he raised to the rank of genera, but he slightly modified their definitions and preferred to use the name Acidaspidae for the family, as is general in Europe, dividing it into four main groups comprising six genera. Raymond,3 in 1916, was led to criticize Clarke's principle of classification, pointing out the unnatural association of species which resulted from its application, and he accordingly desired to alter the definitions of the genera as given in 1913 in the second edition of Zittel-Eastman's “Textbook of Palaeontology ” (vol. i, p. 722). Special attention was paid to the characters of the pleurae, as in Barrande's old scheme.