317 
iipfr&AXHjrrri:. 
arranged in close series ; preoperculum almost or completely covered 
by the cheek-plates; operculum quadrangular, broader above than 
below; suboperculum large, trapezoidal, deeper behind than in 
front, and without an ascending process at its antero-superior angle ; 
branchiostegal rays few and broad, and a very large gular plate 
present, these being comparatively smooth. [Annular ossifications 
in the sheath of the notochord known only at the base of the tail 
in one specimen.] Fulcra biserial, conspicuous on all the fins 
except the dorsal; fin-rays more or less ornamented with ridges 
of ganoine. Pectoral much exceeding the pelvic fins in size, but 
the latter well-developed ; dorsal and anal fins triangular in shape, 
the former opposed to the pelvic pair, the latter small and remote ; 
caudal fin deeply forked. Scales thick and deeply overlapping, 
destitute of an inner rib, but those of the flank with a peg-and- 
socket articulation ; the external layer of ganoine marked with 
deep longitudinal grooves; all the scales much longer than deep, 
but especially elongated in the ventral region ; no enlarged series 
of ridge-scales, but some enlarged on the inner side of the pectoral 
and pelvic fins, three large scales surrounding the anus in advance 
of the anal fin, and some large postclaviculars conspicuous. Lateral 
line obscurely marked, opening on the scales by widely-separated 
vertical slits. 
The character of the external ornament renders it difficult to 
observe the sutures between the head-bones in Ptycholepis ; and the 
dense squamation obscures the endoskeleton of the trunk in all 
known specimens. The inner bones of the head and the inner 
dentition also remain unknown. 
Ptycholepis bollensis, Agassiz. 
1832. Ptycholepis bollensis, L. Agassiz, Neues Jalirb. p. 142 (name 
only). 
1833-44. Ptycholepis bollensis , L. Agassiz, Poiss. Foss. vol. ii. pt. i. p. 11, 
pt. ii. p. 108, pi. lviii. b. 
1849. Ptycholepis bollensis, W. C. Williamson, Phil. Trans. 1849, 
p. 444. 
1852. Ptycholepis bollensis, F. A. Quenstedt, Handb. Petrefakt. p. 203, 
pi. xv. fig. 5. 
1858. Ptycholepis bollensis, F. A. Quenstedt, Der Jura, p. 231, pi. xxx. 
figs. 1-7, pi. xxxi. fig. 8. 
1865. Ptycholepis bollensis , G. Cotteau, Bull. Soc. Sci. Yonne, vol. xix. 
pt. ii. p. 337. 
1875. Ptycholepis barrati, H. E. Sauvage, Bibl. Ecole Hautes Etudes, 
vol. xiv. no. 1, p. 8, pi. ii. fig. 2. [Distorted fish.] 
1891. Ptycholepis barrati, H. E. Sauvage, Bull. Soc. Sci. Yonne, 
vol. xlv. pt. ii. p. 33, pi. i. 
