A. Smith Woodivard — Acrodus Post-Liassic. 103 



of Acrodus exhibit any very close resemblance to the typical forms 

 from the Trias and Lias; and it is therefore of considerable interest 

 to be able to record some most characteristic examples of this dental 

 ^jpe from the Ganlt of Folkestone. The British Museum possesses 

 about nine well-preserved specimens, obtained from the Gardner 

 Collection, and it requires but a brief examination to recognize their 

 distinctness from all previously described species. The teeth are of 

 comparatively small size, and vary considerably in form according 

 to their original situation in the jaw ; examples that are evidently 

 referable to the symphysial area are short, with much-raised crowns, 

 and indications of lateral cusps (Fig. 2) ; while those from posterior 

 positions (Fig. 3) are more elongated and have the coronal surface 



Fig. 2. Fig. 3. 



Figs. 2, 3. Anterior and posterior teeth of Jcrodus levis, A. S. "Woodw. Twice 

 natural size. Gault, Folkestone. [Gardner Coll., Brit. Mus.] 



gently rounded and showing but little elevation. The superficial 

 ornament consists of sharp wrinkles disposed in the ordinary manner, 

 but relatively far apart, and never approaching a reticulate arrange- 

 ment ; and in most cases the rugee do not extend far down upon the 

 sides of the crown, so that there is a noticeable smoothness of the 

 enamel, which suggests the appropriate specific name of levis. 

 Formation and Locality. — Gault — Folkestone. 



A. TRANSVEKsus, Agassiz ("Eech. Poiss. Foss." vol. iii. p. 148, pi. 22, 



figs. 28, 29). 

 A. POLYDYOTios, Eeuss (" Verstein. bohm. Kreideform." pt. ii. p. 97, 



pi. xxi. figs. 1-8). 

 A. CRETACEUS, Dixon ('-Geol, and Foss. Sussex," 1st edit, p. 364, 



pi. XXX. fig. 13). 



There can be no doubt that the species described under the above 

 names are founded upon teeth of Drepanephorus. Agassiz himself 

 admitted (I.e. p. 149) that the first of the three forms exhibited note- 

 worthj' deviations from the typical early Mesozoic species of Acrodus, 

 and miglit be generically distinct; and later discoveries have now 

 established this original surmise as a fact. All the teeth have the 

 characteristic median ridge of those occupying the more posterior 

 positions in Drepanephorus, and there is the same well-marked 

 ornamentation — numerous fine rug£e descending on either side from 

 the ridge and passing more or less abruptly into a complex and 

 delicate network. To the first-named species, which was founded 

 upon teeth from the Maestricht Beds, may probably be referred a 

 well-preserved specimen obtained from the Chalk of Lewes by the 

 late Dr. Mantell, and also one other small fragment from the same 

 locality. The root is not displayed, so that it is impossible to deter- 

 mine whether there is the curious perforation noted by Egerton ia 



