246 
SELACHII. 
not exceed its maximum breadth. The fossil, in fact, is very similar 
to the dermal tubercles of Ilyhodas (PI. VIII. figs. 2, 3), and though 
regarded as a tooth by M‘Coy, L. G. de Koninck, and .1. \V. Davis, 
it may be reasonably assigned to the outer skin, as already suggested 
by Newberry & Worthen, Traiitschold, and Lohest. In accordance 
with this determination, Trautsohold proposes to substitute the name 
of Ostinasjiis for that of Petrodus, as being more appropriate h 
The following examples of Patrodus are comprised in the Col- 
lection : — 
P. 2244. Two tubercles from the Carboniferous Limestone of Derby- 
shire, similar to those in the Woodwardian ^Museum, 
Cambridge, named P. palelliformis, JDCoy The ex- 
serted 2 )ortioii has a pointed apex, and the radiating 
ridges arc about 13 or 14 in number, terminating at the 
base, very strong, sometimes dichotomously branching, 
and sometimes slightly marked by transverse sulci. 
EfjiHon Coll. 
46823-4. Six similar sjiecimcns, and piece of limestone exhibiting 
six others ; Yoredale Hocks, near Todmorden, Lancashire. 
Gilbertson Coll. 
P. 2863. Three almost similar tubercles, of the form named P. occi- 
dentalis, Newberry & Worthen®; Coal-Measures, Belle- 
ville, Illinois. EiuiislcUhn Coll. 
P. 4734. Small example, with comparatively smooth ridges, referable 
to P. harhotanns, II. Ilomanowsky ^ ; Carboniferous Lime- 
stone, Mjatsohkowa, near Moscow, Ilussia. 
Purchased, 1884. 
P. 5855. Smoother tubercle ; Yoredale Hocks, near Todmorden. 
Presented by S. Barlcer, Esq., 1888. 
P. 5116. Hive larger specimens ; Mjatschkowa. Purchased, \SS15. 
P. 4734 a. Two tubercles, oval in shape, not pointed, but with 
‘ Nout. M(Sm. Soc. Imp. Nat. JIoscou, Tol. xiii. (1874), p. 2'.)8. 
® Aim. Mag. Nat. Hist. [2] vol. ii. (1848), p. 132, and Brit. I’aliroz. Foss. (1855), 
p. G."7, pi. 3 0 . figs. 6-8 ; J. W. Davis, Trans. Boy. Dublin Soo. [2] vol. i. (1883), 
I). 400, pi. li. Hg. 16; M. Lobest, Ann, Soc. Gool. Belg. vol. xi. (1883), p. 318, 
pi. iii. figs. 4-0, 1)1. V. fig. 1. 
3 Pal. Illinois, vol. ii. (1866), p. 70, pi. iv. figs. 15, 16. 
s Bull. Soo.Imp.Nat. Mosoju, 1864, pt. ii.p. 164, pi. iv.fig.36; Tubercnle isoU 
dune plaque de I’Asterolepis (?), II. Eoraanowsky, loc. cit. p. 170 ; Ostinaspis har- 
hoiana, 11. Trautsohold, Nouv. Mem. Soo. Imp. Nat. Moscou, vol. xiii. (1874), 
p. 2!)8, pi. xxviii. fig. 12, a-d. 
