37 
space of a millimetre ; and each of these teeth has a stout basal portion, 
becoming suddenly slender at about its middle. The bones of the opercular 
fold have a small antero-posterior measurement, but it is almost impossible to 
distinguish the limits between the different elements ; the operculum, 
hoAvever, is jirobably at least twice as deep as broad, and tlio siibopereulum 
half the size, as suggested by the type-specimen (PL V, Pig. 5). 
Appendicular Skeleton . — All the hn-rays are very robust and closely 
articulated, and fulcra are always distinct. The paired-tins seem to be inserted 
close to the ventral margin; and the pelvic pair is well developed, eacli fin 
having not less than six or seven rays, and its point of insertion not being 
much nearer to the anal than to the insertion of the pectorals. In the original 
of PI. V, Pig. 7, the dorsal tin exhibits fourteen rays, the length of the longest 
equalling that of the base-line as preserved ; and the anal tin is mucb smaller, 
with only twelve or thirteen rays. The jiowerful caudal fin is slightly forked, 
and comprises not less than sixteen rays. 
Squamation . — As usual in the genus, the scales of two series upon 
the middle of the tiauk are much vertically elongated, while the series 
immediately above, and two series below, are also remarkably deep. The 
lateral line crosses the superior third of the upper of the deepest flank-series. 
Bemarks . — The large size of the head and the robust proportions of 
P. crassus render even imperfect examples at once recognizable. 
CLETTimOLEPIS, Eejerton, 1861. 
(Quart. Joum. Geol. Soc., vol. xx., p. 3.) 
Gen. Char.—Jlctxd small ; snout acute ; trunk very deep ; the 
dorsal and anal fins remote and opposite ; dorsal margin in advance of the 
till considerably arched, ventral margin in advance of the liu more gently 
arched ; caudal pedicle short, the upper lobe scarcely produced ; caudal fin 
slightly forked ; pectoral tins large ; pelvic fins present ; scales deep, 
united bj’’ a peg-and-socket arrangement of the anterior tliickened margin ; 
the series between tlie dorsal and anal fins sharply turned forwards for a short 
space aliove and below ; ridge-scales present both dorsally and ventrally. 
Oljs . — This genus was originally founded liy Sir Philip Egerton (loc. 
cit.) upon an imperfect specimen discovered in the Hawkesbiiry rocks of 
Cockatoo Island, and Avas naturally comjjarcd with the late Palteozoic genus. 
