In the British Museum there are several specimens of “papilionaceous” flattened bodies exhibiting six or more concentric lines radiating from two nuclei on either side of an elevated medial line. The stone in which they are embedded is unquestionably the Stonesfield slate; it contains the characteristic Trigonia angulata, Rhynchonella, Ostrea, and Modiola Sowerbyana, D'Orb. (= plicata, Sowerby). The enigmatical bodies to which I now allude are stained of a deep redferruginous colour, the matrix retaining the grey tint and crystalline texture of the Stonesfield slate. On comparison between these remains and those of the specimens of Geomyda spinosa, from Singapore, in the British Museum, presented by Sir A. Smith, a comparison which was suggested to me by Mr. Davies, whose accurate discrimination first threw light upon the nature of the present evidence, I have been led to consider that the specimens in the Fossil Gallery represent the second, third, and fourth median scutes of a tortoise allied to the recent African species. The fossils and their corresponding impressions from the Stonesfield slate afford, according to my interpretation, evidence of the texture of the horny scutes which were developed outside the bony carapace of the old Oolitic tortoise. A particular interest is attached to these specimens, as they were considered by the late Edward Forbes as Trigonellites, or opercula of Ammonites.