308 R. Lydekker — Sordwell and other Crocodilians. 



presented many Alligatoroid features (wliiGh are of course enhanced 

 by the inclusion of A. Eantoniensis in the same species), and that 

 it was difficult to say whether the species should really be included 

 among the Crocodiles or the Alligators. Prof Huxley's observations, 

 which proved the existence of a ventral dermal armour, showed that 

 the Hordwell Crocodilian in this respect differed decidedly from 

 all known members of the genus Crocodilus ; but since such an 

 armour is present in some species of Alligator (including^ Cayman 

 and Jacare) and absent in others, this feature would not of itself 

 necessarily exclude the species from the former genus. Professor 

 Huxley showed, moreover, that in having the upper teeth more 

 numerous than the lower, the species differed from Alligator and 

 agreed with Crocodilus ; while the usual presence of a notch in the 

 skull for the reception of the fourth lower tooth is a character of the 

 latter genus. It will suffice to mention here that the cranium is 

 characterized by the peculiar circumstance that the premaxill^ are 

 united superiorly, and thus separate the nasals from the anterior 

 nares. 



The reader's attention must now be directed to the genus Diplo- 

 cynodon, which was founded by Pomel ^ upon the lower jaw of an 

 Alligatoroid Crocodilian from the Lower Miocene (Upper Oligocene) 

 of AUier, which presented the peculiar feature of having the third 

 lower tooth nearly as much enlarged as the fourth — from which 

 feature the generic name was chosen. To the type specimen Pomel 

 applied the name D. Rateli, and subsequently ^ referred to the same 

 genus the so-called Alligator Santonienns. Subsequently again 

 H. von Meyer* identified with this D. Rateli both a Crocodilian 

 mentioned by Bravard from Allier under the name of Crocodilus 

 elaverensis, and also others from the equivalent beds of Weissenau 

 and other places in the Mayence basin to which he had previously 

 applied the names C. Hatlii, C. JBrucM, C. medius, and C. Brauniorum. 

 At the same time Meyer observed that this form agreed with the 

 so-called Crocodilus Itastingsies in the peculiar relations of the 

 pre-maxillse and nasals; and he consequently came to the conclusion 

 that both were very closely allied, if not specifically the same. 



At a much later period M. Vaillant^ described the Crocodilian 

 remains from Allier and proposed for one form, in which the nasals 

 reach the nares, the name of Diplocynodou gracilis ; retaining that 

 of D. rateli for the type mandible, which he regarded as probably 

 distinct from his D. gracilis. His researches proved that Diplocynodon 

 was furnished with ventral dermal armour. 



In 1877 Herr Ludwig® described and figured the Crocodilians 

 from the Mayence basin, and re-named the form in which the nasals 

 did not reach the nares Alligator Darwini (including in that species the 



^ I follow the views of Dr. Giinther in this respect. 



2 Bull. Sec. Geol. France, ser. 2, vol. iv. p. 383 (1847). 



3 Catalogue Methodique, p. 124 (1853). 

 * Neues Jahrbuch, 1857, p 538. 



5 Ann Sci. Geol. vol. iii. art, 1 (1872). 

 ^ Pal83ontographica, suppl. vol. iii. pt. 4. 



