Head and Opercular Apparatus. — The proportions of the head and 
opercnlar apparatus are shown in No. h, but the only example exhibiting the 
faintest details of strnetnre is the im])erfect specimen, No. c (PI. VI, Pig. 1). 
The roof of the skull is extended by membrane bones well oyer the oper- 
ciilnm ; the orbit is large, and the two postero-superior elements of the well- 
developed snb-orbital ring are evident. The preoperenlimi appears to have 
been absent, and the oi)erculuin and snlioperculum have a short antero- 
posterior measurement ; the jirccise position of the sntnrc l^ctween the 
two latter elements is nncertain, though it is probably the lower of the 
two transverse lines indicated in tlic tli>rnre. 
O 
Appendicidar Skeleton . — Portions of the paired fins are in’cserved 
in the type-specimen (PI. V, Pig 1), both exhibiting much elongated 
slender rays ; and the pelvic tins are placed much behind a point liaif- 
way between the opercular apparatus and the anal tin. As just mentioned, 
tlie dorsal and anal fins (PI. V, Pig. 1 ; PI. VIII, Pig. 1) arc almost equal in 
size, and the former arises slightly in advance of the latter ; the length 
of the longest rays in the anal is greater than the extent of the base-line, 
■while in tlic dorsal the same is almost the case ; and in the first-mentioned 
tin there arc twelve or thirteen rays, wliile in the dorsal this number is only 
exceeded by one or two. The caudal fin is beautifully preserved and slightly 
forked, consisting of about sixteen to twenty rays ; and its upper and lower 
margins, like the anterior margins of the dorsal and anal, arc fringed with 
delicate fulcra. The fin-rays are well spaced, and in all the fins they appear 
to be closely articulated and soon bifurcating. 
Squamation. — The scales of two scries upon the middle of the anterior 
portion of the flank are in part four times as deep as broad, and, as shown by 
No. c (PI. VI, Pig. 1), the lateral line traverses the uppermost of these, 
dividing each scale unequally in the ordinary manner. Above and below 
tlic two principal scries just mentioned, the scales are much deeper than 
broad in two other scries, and it is only towards the extremity of the caudal 
region that they appear to become equilateral. The sharply-pointed dorsal 
and ventral ridge-scales arc also distinctly recognizalile. 
llemarks. — Prom the sj^ecies described below, P. gracilis is distinguished 
by its more slender proportions, and the great elevation of the dorsal and anal 
tins. 
