B. Lydekker — On Hylceochamfm. 513 



In respect, however, to the serial position of Hylceocliampsa, there 

 is no question whatever but that it must be regarded as one of the 

 most specialized members of the Goniophiloid Crocodiles, and from 

 the backward position of the posterior nares and the small size of 

 the supratemporal fossae that it is probably allied to Bernissartia. 

 In my original paper I purposely refrained from quoting Sir R. 

 Owen's description of the orbito-temporal region of HylceocJiampsa, 

 because, either from being misled by the broken edges of the bones 

 in this region, or from not having at that time directed his attention 

 to the importance of the features of this part, the Professor's descrip- 

 tion is not altogether satisfactory ; ' but the fact is undoubted that 

 Hylceocliampsa has the orbit in as complete communication with the 

 lateral or infratemporal fossa ^ as in Crocodilus itself. 



Assuming that HylcBOchampsa be distinct from Bernissartia, the 

 question will then arise whether the procoelous vertebrae of a small 

 Crocodilian from the Wealden both of Sussex and the Isle of Wight 

 described by Prof. Seeley in the Quart. Journ. Geol. Soc. vol. xliii. 

 p. 212, pi. xii. figs. 7-8, under the name of Heterosuchus valdensis, 

 may not belong to the former genus. This view occurred, indeed, 

 to me at the time of writing my above-mentioned paper ; but being 

 then unable to distinguish Hylceocliampsa from Bernissartia (in 

 which the vertebrae are amphicoelous), it could not be advanced. 

 In favour of it we may observe that it is highly improbable that the 

 transition from the amphicoelous to the procoelous type of vertebras 

 precisel}'^ synchronized with the union of the pterygoids beneath the 

 narial passage, and therefore that it is highly probable that Hylceo- 

 champsa, in which the posterior nares are only one step removed 

 from the most specialized type, may have had procoelous vertebrae. 

 I cannot, of course, put forward this suggestion as anything more 

 than a possible, or perhaps probable, contingency ; but it clearly 

 shows how undesirable it is (as I hope shortly to show on another 

 occasion) in the case of any particular group to form one genus on 

 portions of the skeleton which are totally unknown in one already 

 described. 



Finally, I may observe that in the scheme of classification given 

 on page 312 of my paper I proposed the name Crocodilia Vera for 

 the united Eusuchia and Mesosuchia of Prof. Huxley ; on further 

 consideration, however, the term Eusuchia appears such a convenient 

 one in opposition to Parasuchia, that I think it preferable to retain 

 this old and well-known name in a wider sense, than to substitute 

 for it the new one proposed. 



1 In his reply, M. DoUo enlists Mr. A. S. "Woodward on the side of the Teleosauroid 

 nature of Hylceochampsa ; but I am authorized to state that the latter writer merely 

 followed the lead of Sir R. Owen in this respect, and that having examined the 

 specimen with me when I was writing the original paper, he was fully convinced of 

 the relation of the orbit to the infratemporal fossa being of the type obtaining in the 

 Crocodilidce. 



2 By an inadvertence on p. 310, line 29 from top, of my paper, the words " cJiez 

 celui-ci " are omitted at the conclusion of the quotation from M. Dollo ; an omission 

 which alters the sense of the whole passage. 



DKCADE III. VOL. IV. NO. XI. 33 



