Sir Philip Grey-Egerton — On some New Pycnodonts. 53 
sketches of three Pycnodont mandibles which I considered could 
not all be referred to Pycnodns toliapicus. For thirty years the 
subject escaped my memory, until the examination of the Folkestone 
specimen described in a previous article reminded me of the 
occurrence, and induced me to make a comparison between it and 
the Bowerbankian specimens now in the British Museum. Two of 
these belong no doubt to Pycnodus toliapicus. They are right and 
left mandibles, and so nearly of a size that they might have belonged 
to the same individual. The right jaw lias three rows of teeth. 
Tliose of the inner row are the largest. They are five in number 
and elliptic in form, agreeing in the latter respect with the descrip- 
tion given by Agassiz : “ The principal teeth are elongated and 
rounded at the extremities.” The second row contains six teeth 
very much smaller than those of the inner row, and of ovoid out- 
line ; the third row has four teeth of similar figure to the preeeding 
ones, but rather smaller. The left mandible corresponds in these 
details with the right, but has in addition an inner row of small 
teeth between the principal row and the symphysis, of which three 
anterior ones are apparently in situ. The occurrence of this inner 
row of den ticles is not in my opinion of specific signification when 
the other characters correspond so closely. It is constantin Gyrodus, 
but in Pycnodus, as I have before stated, it is by no means a charac- 
teristic feature. When it is present the component teeth are invariably 
smaller than any others. On comparing these specimens and the 
figure of Pycnodus toliapicus given on pl. 72 a. fig. oo, of vol. ii. 
pt. 2, of the Poissons Fossiles, with the figure of Periodus Kcenigi , 
figs. 61-2 on the same plate, and the specimens in the British Museum 
and my own cabinet, I am at a loss to discover any difierence either 
generic or specific between them. The specimens of Periodus have 
been more rubbed down by use, and the discrepancy in the form of 
the crowns is due to the unequal attrition of the vomerine teeth. 
The third specimen from Dr. Bowerbank’s collection is a right 
mandible in beautiful preservation. It is quite as large as Coelodus 
ellipticus described above, and contains three rows of teeth. The 
inner or principal row (Pl. III. Fig. 2 a) has five normal teeth in 
series and a sixth, the anterior one, replaced by what I have 
designated a twin tooth (Pl. III. Fig. 2 t). The regulär teeth of 
this row are larger and more obtusely oval than those of Pycnodus 
toliapicus. The twin tootb is divided into a circular denticle, rather 
irregulär, and a crescentic portion embracing the inner periphery of 
the former. I have already alluded to this dentary sport as being 
not uncommon in some of the Pycnodont genera. The second series 
(Pl. III. Fig. 2 b ) comprises eight teeth, which, although considerably 
smaller than the principal grinders, are nevertheless comparatively of 
larger size than those of Pycnodus toliapicus. They are elliptic in 
form, differing also in this respect from the oval teeth of that species. 
The outer row (Pl. III. Fig. 2 c ) contains six teeth very much 
smaller and nearly circular; the crown or triturating surface of those 
not yet come into use is irregulär ly puckered. It will be gathered 
from these details that the species is well characterized and broadly 
