59 
The general proportions of the cartilages are so well shown 
in Fig. 1, that they do not require any detailed description ; 
and the principal features are pointed out by the lettering. 
The cranium is relatively short and robust, and appearances are 
suggestive of no great prolongation of the snout in advance of 
the mouth, while the latter would probably he almost as 
terminal as in Cestracion. The position of the left orbit (orb.) 
is well marked, and the outlines of the left postero-lateral angle 
of the cranium (pfa.) are distinct; the large fontanelle (. fo .) in 
the anterior portion of the cranial roof is also shown. The 
superior boundary of the upper jaw (pterygo-quadrate ), of which 
the hinder extremity is marked ptq. 9 is unfortunately obscure ; 
but the left mandibular cartilage (md.) is complete, and of 
considerable depth in its hinder portion. 
Most of the teeth exhibited are so much obscured by matrix 
that they cannot well be separately described; but they are all 
little disturbed from their original positions, and so make known 
(for the first time in the typical Hybodus) the number of the 
antero-posterior series. 
In the mandible (Fig. 2,) there is no median symphysial row 
of teeth, and the number of series on the fully-exposed left side is 
ten (i.—x.), with qios-sib/y an eleventh minute row, indicated by 
some broken fragments. So far as preserved, no series exhibits 
more than five components ; and the largest teeth are those of 
nos. y. —vn. The latter, and all situated in advance of them, 
are very robust, with a comparatively high, conical, median 
cusp, and three or four large lateral cusps; the coronal surface 
being marked by numerous radiating wrinkles, the outer lower 
margin prominent and coarsely crimped, and the inner lower 
margin somewhat channeled for the overlapping of the tooth 
immediately within. Of the lower series viii. and ix., the 
teeth are relatively longer than these, with less elevated and more 
obtuse crowns; and of series x., the teeth are comparatively 
minute, with a single broad coronal eminence, marked by few 
superficial wrinkles, and with a single insignificant denticle at 
each extremity. 
In the upper jaw there are also indications of nine or ten 
transverse dental series, though it is not easy to determine their 
characters. However, by combining the information afforded 
