MTLIOBATIDa. 
161 
In the Collection there are also similar teeth and fragments from 
Burham (41697), Greenhithe (P. 5452), Bromley (41698), and 
Dover (35871, 35875, 47285) in Kent, besides from localities in 
Sussex (28389), and from 'Warminater, Wilts (46394). 
The following vertebrce are of the same type as those associated 
with the group of teeth of Ptychodus decurrens referred to above 
(no. 39436). As already remarked, a similar vertebra has been 
described in detail by C. Hasse, under the name of Selache dav- 
i[e']si. The radiating lamellae are merely represented by faint lines 
upon the “ central double-cone,” while the concentric lamellae are 
numerous and well developed ; these vertebrae thus appear to the 
present writer to be truly “ tectospondylic,” and quite comparable 
with those of Myliobatis, only differing from the latter in the 
presence of small uncalcified areas having the form of an X when 
viewed in transverse section. 
4214-5. Two small series of imperfect vertebrae ; Chalk, Sussex. 
ManteU Coll. 
P. 4641. Broken specimens in chalk, one partly shown in transverse 
section, and others in longitudinal section ; Sussex. 
Enniskillen Coll. 
33295. Large imperfect vertebra ; Gravesend, Kent. 
Presented by M. Wright, Esq., 1868. 
49016. Vertebra and fragments; Kent. Mrs. Smith’s Coll. 
40644. Detached specimen much broken, enclosed in flint ; Chalk, 
Norwich. Presented by W. Firth, Esq., 1864. 
The following species of Ptychodus have also been founded upon 
detached teeth, but there are no examples in the Collection : — 
Ptychodtis janevaii : Sporetodus janevaii, E. D. Cope, in Hayden’s 
Bulk U. S. GeoL Surv. Territ. no. 2, 1874, p. 47. 
P. janewayii, E. D. Cope, Vert. Cret. Form. West (U. 8. 
Gcol. Surv. Territ. 1875), p. 244. — Cretaceous (Niobrara 
Epoch) ; Kansas, IJ.S.A. 
Ptychodus occidentalis, J. Leidy, Proc. Acad. Nat. Sci. Philad. 
1868, p. 207 ; also Extinct Vert. Fauna West Territ. 
(U. S. Geol. Surv. Territ. 1873), p. 298, pi. xvii. figs. 7, 
8, pi. xviii. figs. 15-18. — Cretaceous (Niobrara Epoch) ; 
Smoky Hill, Kansas, IJ.S.A. 
