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Show 1888.] ANATOMY OF THE MESOSUCHIA. 431 as praepubis. Further, Prof. H. G. Seeley homologizes this praepubis with a bone having similar relations to the other elements of the pelvic girdle thought to be present in Ornithosauria. But C. K. Hoffmann has abandoned his earlier interpretation of the bone, and he, in a more recent publication, says that he now considers as pubis the bone which once he regarded as praepubis (36). Prot. H. G. Seeley finds that the bone commonly accepted as the Crocodilian pubis is much more slender, and it is much less expanded at the anterior end in all the species from the Lias and Lower Oolite rocks; and he refers to " some undescribed types in the collection of A. Leeds, Esq., in which it is reduced to a mere bony style without expansion at either end, comparable in form and substance to a lucifer match" (37). It is manifest that the bone here described by Prof. H. G. Seeley in the above quotation cannot be identified with that bone which, from its constant association with the other pelvic bones, and from its close resemblance to the Eusuchian pubis, I have described and figured as the os pubis of these Peterborough Mesosuchians. Although I have some knowledge of Mr. Leeds's collection, I have not seen in it such pubic (prcebubic, S.) bones with undilated ends; and Mr. Leeds assures me that he has not any such as those to which Prof. Seeley refers. The only bones in the collection at all corresponding to Prof. Seeley's description, I have ventured to interpret as the detached styliform atlantal riblets. R. Owen, referring to a Liassic Teleosaur preserved in the Whitby Museum, writes, "Both ischium and pubis are relatively more expanded than in the Gavial " (38). In the Liassic Crocodilians, so far as these are known to me, the ossa pubis are similar in form, they have similar connections, and they are essentially identical with the ossa pubis of the Eusuchia, As regards the pelvic element in Ornithosauria, by some authors termed prapubis, with which Prof. H. G. Seeley (in this matter following Quenstedt) homologizes this Crocodilian bone, I have for some time had doubts of its existence as a separate, distinct element. In illustration of the view he adopts concerning it, Prof. Seeley reproduces Quenstedt's representation of the bones in question, as displayed in Quenstedt's plate of Ptercdactylus (Cycnorhamphus) sue-vicus (39). But these parts are, I suggest, susceptible of another reading; the paddle- or fan-like bone as H. v. Meyer described it, with narrow short shaft and expanded opposite end, is not, I submit, a bone complete in itself, but merely the ventral symphysial portion of an os pubis constructed and associated with the other pelvic elements after the common Lacertilian plan. Quenstedt's figure represents the two paddle-like pieces detached from their connections, flatly extended, as he conceived their natural position beneath the abdomen, in advance of the acetabulum (43). My first suspicions of the inaccuracy of this arrangement were aroused by observing that in those figures of Pterodactyles given by H. v. Meyer in his ' Rept. a. d. lith. Schiefer,' in which both ossa pubis (praepubis) are displayed in side or oblique view, the right or left bone (as the case 30* |