174 
ACTINOPTERVGII. 
consisting of distally bifurcating rays, all with large A-shaped 
fulcra; pectoral fins much larger than the pelvic pair; dorsal fin 
arising at the angulation of the back, extending to the caudal 
pedicle, high in front, becoming low behind; anal fin small; caudal 
fin forked. Scales covering the whole of the trunk, in regular 
series, united by peg-and-socket articulation, and more or less pec¬ 
tinated at the hinder border; the scales of the middle of the flank 
and of the dorsal region much deeper than broad, with more or less 
convex hinder border ; those of the ventral region at least as broad 
as deep; postclavicular scales very large ; the ridge-scales of the 
caudal pedicle not much enlarged. 
Histionotus angularis, Egerton. 
1854-55. Histionotus angularis, Sir P. Egerton, Ann. Mag. Nat. Hist. 
[2] vol. xiii. p. 434, and Pigs. & Descript. Brit. Organic Remains 
(Mem. Geol. Surv.), dec. viii. no. 5, pi. v. 
1889. Histionotus angularis, J. 0. Mansel-Pleydell, Geol. Mag. [3] 
vol. vi. p. 241, pi. vii. 
Type. Eish, wanting tail; British Museum. 
The type species, attaining a length of about 02. Length of 
head with opercular apparatus very slightly exceeding its maximum 
depth, and occupying about one-quarter of the total length of the 
fish; length of the trunk equalling twice its maximum depth, and 
the dorsal angulation measuring approximately 148°. The head and 
opercular bones externally ornamented with fine, closely arranged 
rugse; the large postclavicular plates similarly ornamented. Ein- 
rays stout and smooth ; pectoral fins scarcely twice as large as the 
pelvic pair, and the latter arising in advance of the middle point of 
the trunk; dorsal fin consisting of at least 25 rays. Pectinations 
of the scales delicate and confined to their hinder margin, but con¬ 
spicuous in all regions of the trunk. 
Form. &f Log. Purbeck Beds : Dorsetshire and Wiltshire. 
P. 577. Type specimen, described and figured by Egerton, loc. cit.; 
Swanage, Dorsetshire. The impression of the caudal 
region is much less distinct than indicated in the published 
figure, in which the anal fin is erroneously extended. 
Egerton Coll. 
P. 3614. Crushed head and trunk, wanting the greater part of the 
caudal region; Swanage, EnnisJcillen Coll. 
P. 5935. Small fish somewhat distorted and with imperfect fins, 
but displaying the bifurcation of the caudal; Swanage. 
