All the skulls named _Crocodilus palustris_ which I have seen are referable either to _C. biporcatus_ or to _C. bombifrons_. With respect to the _C. palustris_ of Lesson and Duméril and Bibron, the latter authors consider it to be only a variety of _C. vulgaris_. Their description would, however, apply very well to _C. bombifrons_, as I have defined it above; and they expressly state ('Erp. Générale,' t. iii. p. 113) that all their specimens (twelve in number and varying in length from 30 centimetres to more than 3 metres) came from the East Indies or the Seychelle Islands. Now, Duméril and Bibron enumerate only three Asiatic Crocodiles--_C. biporcatus_, _C. palustris_, and _C. galeatus_, the last of which was only known to them by description; so that all the numerous Asiatic crocodiles which passed through their hands belonged either to _C. biporcatus_ or _C. palustris_. On the other hand, all the skulls of crocodiles from Asia which I have met with (amounting to at least twenty) are either those of _C. biporcatus_ or of the species which I have called _bombifrons_; so that I suspect the latter title will turn out to be a synonym of _palustris_. 6. _Crocodilus rhombifer._ I have not been able to obtain any skull of this species, which, according to Cuvier's account and figures ('Oss. Fossiles,' t. ix. p. 102), resembles _C. Americanus_ in the great convexity of its nasal region, but differs from it in the greater breadth of the skull, and in the strong converging preorbital ridges, which appear to be limited to the lachrymal bones. If the figures are to be I trusted, however, there are other very important distinctive characters about the cranium of this species; for Cuvier's, fig. 2, pl. 331, which gives a view of the palate, shows the premaxillo-maxillary suture forming a nearly straight transverse line. * * * * * There remain several species of _Crocodilus_ whose skulls I have not been able to examine, and of which no sufficient descriptions exist. Of these, (7.) _C. galeatus_ and (8.) _C. Gravesii_ (_planirostris_) would appear to be very distinct forms. (9.) _C. marginatus_ is considered by Duméril and Bibron to be only a variety of _C. vulgaris_; and they take the same view of (10.) _Crocodilus suchus_. Professor Owen, however, has figured the cranium of an Egyptian mummy under this name ('Monograph on the Reptilia of the London Clay,' Pal. Soc., 1850). In the under-view of this skull (tab. i. fig. 2), the junction of the premaxilla and the maxilla in the palate seems to be broken away; but on the left side, the palatine process of the maxilla is entire, as far as the level of the anterior margin of the sixth tooth, and there is not a trace of a suture behind this point. Are there, then, two or more species of Crocodile in Egypt, as Geoffroy St.-Hilaire supposed?