PYCNODONTIDJE. 
219 
49147. Plaster cast of type specimen ; Eichstadt. Purchased , 1878. 
37023. A fine specimen, in counterpart, with crushed head and 
wanting part of the ventral margin ; Solenhofen. The 
best side of the fossil is shown of one-half the natural 
size in PL XY. fig. 1, with some parts restored from the 
opposite side. The hones of the cranial roof are shown 
to be especially thick and marked with a relatively 
coarse tubercular ornament. The facial bones are remark¬ 
ably delicate and finely tuberculated, exhibited as very 
irregular large tesserae below the orbit, and represented 
by the remains of one long narrow plate (x) above 
the upper jaw. The sclerotic of the eye is ossified ( scl .). 
The margin of the vomer ( vo .) is exposed in the upper, 
and that of the splenial (spl.) in the lower jaw, both 
of these bearing stout teeth on moderately elongated 
pedicles ; and the external face of the mandible is com¬ 
pleted by the tuberculated dentary (d.) and angular ( ag .) 
plates. The postero-superior portion of the mandible, 
however, is obscured by the thin facial bones. Still 
further below the skull are two elements which seem to 
be identifiable as ceratohyal ( [ch .) and hypohyal (%•); 
both very small, and the former remarkably deepened 
behind. Among the remains of branchial and branchio- 
stegal apparatus, the calcified gill-filaments (fig. 1 a) are 
especially conspicuous, each exhibiting a widely spaced 
series of very fine denticles on its upper margin. Frag¬ 
ments of the operculum (op.) indicate that this plate was 
as coarsely tuberculated as the cranial roof; so also, in 
part at least, was the preoperculum (p.op.), which is dis¬ 
played almost entirely from its inner aspect, and seems 
to be bounded below in the counterpart of this fossil by 
one or perhaps two branchiostegal rays. Below the oper¬ 
cular apparatus are observed very small, tuberculated, 
imbricating scales, which are more or less lozenge-shaped 
and broader than deep, and extend as a covering between 
the rami of the mandible. The neural spines ( n .) of the 
vertebral axis are exhibited enveloped in the squamation, 
those in the abdominal region thickened and extending 
almost or quite to the dorsal ridge. As shown by im¬ 
pressions in the counterpart, they are about 30 in number 
to the base of the caudal pedicle. Immediately behind 
the opercular apparatus are remains of the clavicle, orna¬ 
mented with large tubercles on its lower expansion (cl.); 
