432 PEOF. T. H. HUXLEY ON STAGONOLEPIS EOBERTSONI, 



aquatic than the Teleosaurians, and which probably hannted the 

 estuaries and lakes of the Jurassic epoch. 



In the present paper I have endeavoured to confine myself to the 

 statement of verifiable facts, and to the conclusions obviously sug- 

 gested by them ; and I abstain, for the present, from dwelling on 

 the bearing of these facts and conclusions on the relation of the 

 Grocodilia to other Eeptilia, especially the Ornithoscelida ; but I hope 

 to take up that subject on some future occasion. 



After the preceding pages were written, it occurred to me that a 

 fragment of a Crocodilian skull from the Wealden of Brook Point, in 

 the Isle of Wight, which has been for many years in the Museum 

 of Practical Geology, might possibly yield some information as to 

 the condition of the secondary posterior nares in the Crocodilia of 

 that epoch. The region in which these apertures should occur was 

 thickly covered with matrix; but when the latter was removed, 

 very skilfully and carefully, by Mr. Newton, Assistant Naturalist in 

 the Museum of Practical Geology, it revealed the palatine and 

 pterygoid bones, with the base of the skull behind them, in an almost 

 uninjured state (Plate XIX. fig. 3). 



Nothing could be more instructive than the condition of these 

 parts. The nasal passage is narrower, and the posterior palatine 

 foramina are larger, in proportion to the width of the skull, than in 

 any hitherto known Mesosuchian; the lateral processes of the 

 pterygoids are broader, and the distance between the median 

 Eustachian aperture and the anterior margin of the secondary 

 posterior nostrils far less than in any. The secondary posterior 

 nares themselves are situated relatively further back, and have not a 

 third the dimensions they possess in Steneosaurus or Metrio- 

 rhynclius. The distance between the posterior margins of the 

 lateral processes of the pterygoids and the occipital face of the skull 

 is greatly less. On the left side, the descending process of the post- 

 frontal, which bounds the orbit behind, is seen. The sculpture 

 upon its outer surface is interrupted close to its ventral end, leaving 

 a smooth narrow groove between the orbit and the temporal fossa, 

 which answers to the much broader groove between the orbit and 

 the temporal fossa in the Eusuchia. In all these respects, this 

 "Wealden Crocodile approaches the Eusuchia much more closely 

 than any previously known Mesosuchian Crocodile does ; but it 

 keeps its Mesosuchian character in the manner in which the narrow 

 elongated oval secondary posterior nares are formed. In fact, they 

 are bounded in front by the extreme posterior edge of the palatal 

 plates of the palatine bones, and the pterygoids form only the lateral 

 walls and the septum between the two. The structure therefore 

 lies on the boundary line between that characteristic of the Mesosuchia 

 and that which distinguishes the Eusuchia; and as it constitutes a very 

 good generic distinction, the Wealden Crocodile might be made the 

 type of a new genus, if we could compare it with Goniopholis and 

 Macrorhynchus. Unfortunately there are no well-preserved teeth, 

 and the greater part of the rostrum is absent, while we know 



