CESTRACIONTIDiE. 265 
hinder portion of the abdominal region, where the axial 
skeleton abruptly terminates in the fossil, a series of about 
nine broad elongated cartilages (na ?) occurs higher upon 
the slab, with the appearance of having all the superior 
extremities fused together ; and this may be interpreted, 
either as a displaced portion of the axial skeleton itself, or 
as the support of a dorsal fin. Both the dorsal fin-spines 
are much broken, the anterior (els'.) being situated very 
far forwards, and the posterior being entirely detached 
from the slab. The back of the anterior spine is not quite 
flat, but raised into a slight median longitudinal keel, upon 
which are fixed two sparse series of large denticles. 
Purchased, 1881. 
41103. A large slab of Lias exhibiting the greater part of the left 
pterygo-quadrate (ptq.) and mandibular ( mcl .) cartilages, 
side view (PI. IX. fig. 1), with the dentition, scattered 
shagreen, and three imperfect displaced “ Sphenonchi.” 
The outer teeth of each transverse series in both jaws are 
nearly all in position, and there thus appear to be eight 
series in each ramus, without a median symphysial row, 
as shown by the figure. There are also numerous other 
scattered teeth, exhibited from various aspects. In the 
lower jaw, the first tooth (i.) has much the highest and 
most prehensile crown, there being two large and perhaps 
one small lateral denticle. The second tooth (it.) is some¬ 
what more elongated, witli smaller lateral denticles; and 
in the teeth beyond, the denticles become very insignificant. 
The teeth of series iv. and v. are the largest, and the 
hindermost are much the smallest. In the upper jaw the 
most anterior teeth are much displaced, and there is a 
close general correspondence with the lower dentition, 
those teeth nearest the symphysis only differing from the 
opposing teeth in their relatively larger size. 
Purchased, 1868. 
P. 2199. Group of scattered large teeth, mostly of the typical form, 
but some with unusually prominent lateral cusps. 
Egerton Cod. 
36878-81, 38539-40. Twenty teeth, some with cleft summits, one 
of the latter shown, of the natural size, in PI. IX. fig. 2. 
Purchased , 1862, 1864. 
Egerton Coll. 
P. 2200. About twenty-five teeth. 
