I am indebted to W. Reed, Esq. of York, for the opportunity of making a notice of this species, which closely resembles _O. capito_. * * * * * The species which follow were separated in the "Index to the Ornithosauria," &c. as a different genus. That proposal might still be sustained, for these massive truncated jaws are unlike the spear-shaped jaws of many of the species. And to the minds of some readers the forms already described will arrange themselves in groups which not improbably indicate genera. But a re-examination of the type _Pterodactylus simus_ (Owen) has convinced me that it is a _lower jaw_, and therefore it affords no evidence of the presence or absence of the peculiar front premaxillary teeth which characterize nearly all the Cretaceous species. XXV. Ornithocheirus simus (Owen). Case. Comp. Specimen. =J= _c_ 16 The palate is 2-3/4 inches long, and at the second pair of teeth about 7/8ths of an inch wide. It is fractured at the end through the fifth socket, and at the side along the palatal groove. The first pair of teeth is smaller and closer together than the others. The palatal interspace between the second pair is 3/8ths of an inch; between the third pair, which are large teeth, it is 1/2 an inch. The sockets are sub-circular, and are not separated from each other by wider interspaces than their own length. In front is a long triangular rugose area, convex from above downward, a distance of 1-1/2 inch; and concave from side to side, a width above of rather more than 1/2 an inch. Below this the flattened sides converge to a blunt keel; where, fractured, the jaw is 2-1/2 inches deep. There are several fragments of species allied to the last; one has the triangular area in front very small, only half as high as in the type and very narrow, for the sides are gently rounded into it. It is marked by short longitudinal furrows, impressed vessels I think, while in O. simus the surface is irregularly rough. The first pair of teeth are much larger than in O. simus; they are longer, more conical, and circular, and separated by as wide a space as the second pair. There is not much to found a species on, but as it appears to be quite distinct from O. simus, it is named _O. Carteri_. Another fragment, with the area very long, is marked _O. platyrhinus_. But a sufficiency of species has been indicated to make known the Ornithosaurian fauna of the Cambridge Greensand. And the detailed description of critical types and of the other parts of the skeletons is beyond the general osteology of the tribe, and will rather belong to a memoir in which this flock of Pterodactyles will be restored to their living forms. * * * * *