A. Smith Woodward — Acrodus Post-Liassic. 101 



III. — Notes on Some Post-Liassic Species op Acrodus. 

 By A. Smith Woodavard, F.G.S., F.Z.S., 

 of the British Museum (Natural History). 

 CJO little is known of the extension through later Mesozoic deposits 

 O of Selachian teeth belonging to the familiar type of Acrodus, 

 as represented in the Lias, that any additional evidence upon the 

 subject is invested with considerable interest. It is impossible, of 

 course, from these isolated relics, to determine whether the original 

 Sharks were as closely allied as the resemblances in their dentition 

 might at first lead one to suspect ; in one case,^ indeed, it has been 

 proved that the complete fish differs much from the Liassic species ; 

 but the persistence of the dental type is at any rate of some signifi- 

 cance, and it may therefore be acceptable to offer a few notes upon 

 the undescribed Jurassic and Cretaceous Acrodonts preserved in the 

 British Museum. These specimens furnish evidence of at least two 

 new specific modifications, and they are also suggestive of novel 

 points in regard to some of those already known. 



Acrodus leiodus, Agassiz, MS. 



1844. A. Modus, L. Agassiz, " Rech. Poiss. Foss." vol. i. p. xxxiii (name only). 

 1871. Acrodus, J. Phillips, " Geol. of Oxford," p. 177, fig. 10. 



In the recently acquired collections of Sir Philip Egerton and the 



Earl of Enniskillen, there are several teeth from Stonesfield bearing 



the name of Acrodus leiodus in Agassiz' own handwriting ; and 



these may consequently be regarded as the types of the species 



intended to be so described in one of the projected supplements of 



the "Poissons Fossiles." The form, however, appears to have 



remained hitherto undefined, and the only allusion to it that I have 



succeeded in discovering occurs in Prof. Phillips' work quoted above. 



The Egerton specimens (No. P. 2134) are very unsatisfactory — two 



being much broken, and the third somewhat waterworn — but two of 



those in the Enniskillen Collection (No. P. 2753) and others in the 



Museum are in a comparatively good state of preservation. The 



species is but a small one, as indicated by the annexed woodcut 



(Fig. 1), whicb is twice natural size, and the teeth vary considerably 



in shape, according to their original situation 



in the jaw ; some are much elongated and 



relatively narrow, being referable to a posterior 



position, while others, evidently pertaining to 



Yi^.l.Hooi^ot Acrodus the symphysial area, are notably short and 



leiodus, Ag. Twice broad. It is interesting to remark, also, that 



natural size. Great even the latter are destitute of any prominent 



Oolite Minchinhamp- ^■^^:^^^ ^f ^y^^ coronal surface, and there are 



Mus.] ^ut slight traces of lateral points or cusps. 



All the less abraded examples show a very 



characteristic surface-ornament, consisting of large and rounded 



ridges, closely approximated, and disposed in the ordinary manner ; 



1 A. Wagner, " Monographie der fossilen Fische aus den lithographischen Schiefern. 

 Bayerns," Abh. k. bayer. Akad. d. Wiss. cl. ii. ; vol. ix. pp. 300-304, pi. v. fig. 1. 



