4b ACTINjOPTERTGII. . , . -r 
Iscliyrhiza mii'ci, J. Leidy, ibid. (1856), p. 22^.—Cretaceous 
Greeusand; Burlington Co., Xew Jersey. [The type 
species. Toot^."^^ ; 9\, 7/. 
Isckyrhiza (?) radiata., W. B. Clark, Bull. IF.S. Geol. Surv. 
no. 141 (1896), p. 60, pi. vii. figs. 2 a-c. —Eocene ; Clifton 
Beach, Maryland. [Hypural and caudal vertebrae; Johns 
Hopkins University.] 
Oricardinus tortus., E. D. Cope, Proc. Amer. Phil. Soc. vol. xvii. 
(1878), p. 177.— Upper Cretaceous; Kansas. [Max-illu, 
and vertebrae ; Cope Collection.] 
Genus BSOCiEiLOPS^ nov. 
Syn, Hurygnathus, L. Agassiz, Rep. Brit. Assoc. 1844 (1845), p, 307 
(name only, non F^urygnat hits, Wollaston, 1853). 
A genus known only by the head, which is both depressed and 
elongated. Erontal bones extending close to the occipital border, 
bent into a slight depression in their hinder portion ; parietal bones 
very small. Mandible comparatively short, and gape of mouth not 
extending to the hinder border of the orbit; mandibular teeth 
stout and conical, laterally compressed, well spaced. Operculum 
simple ; branchiostegal rays at least 15 in number; gular plate 
extending for not less than three-quarters the length of the 
mandible. 
Esocelops cavifrons, sp. nov. 
[Plate III. figs. 1, 2.] 
1845. Eurygnathus cavifrons, L. Agassiz, Rep. Brit. Assoc. 1844, 
p. 307 (name only). 
Type. Imperfect head; British Museum. 
The type species, with skull attaining a length of about OT. 
Maximum width of occiput exceeding the length of the postorbital 
region, and somewhat less than one half the length of the cranium. 
Length of mandible about equal to the distance from the end of the 
snout to the hinder border of the orbit. Bones of cranial roof 
slightly rugose or pitted; cheek-plates very delicate, ornamented 
with rounded radiating ridges. Operculum somewhat deeper than 
broad, and its width equalling about one third the length of the 
cranium ; gular plate widest and spatulate behind, its maximum 
width slightly exceeding one third of its length. 
Form. Loc. Lower Eocene (London Clay) : Sheppey, Kent. 
