PLAT Y S0ATAT1D2E. 
541 
Cheirodopsis geikiei, Traquair. 
1881. Cheirodopsis geikiei, 11. H. Traquair, Trans. Roy. Soc. Edinb. 
vol. xxx. p. 56, pi. v. figs, 17-19. 
1890. Cheirodopsis geikiei , R. H. Traquair, Ann. Mag. Nat. Hist. [6] 
vol. vi. p. 494. 
Type. Imperfect fish, wanting paired and caudal fins ; Geol. 
Survey of Scotland, Edinburgh. 
The type species, of small size. Head relatively large, it with 
the opercular apparatus probably measuring more than one quarter 
of the total length of the fish ; external bones ornamented with 
coarse, tortuous, and reticulating corrugations. Scales with an 
especially coarse ornament. 
This species cannot be satisfactorily defined until the discovery 
of more completely preserved specimens. 
Form. Sf Loe. Calciferous Sandstones (Cement-stone Group): 
Eskdale, Dumfriesshire. 
P. 4056. Remains of two small fishes, one showing parts of the 
median fins. Purchased , 1883. 
P. 4084. Imperfect large specimen, wanting the tail and the greater 
portion of the head, and with fragments only of the 
dorsal and anal fins. The length of the trunk from the 
pectoral arch to the end of the caudal pedicle must have 
been originally about 0*06. Purchased , 1883. 
Genus PLATYSOMUS, Agassiz. 
[Poiss. Foss. vol. ii. pt. i. 1835, pp. 6, 161.] 
Syn. Uropteryx, L. Agassiz, MS. in collections. 
Trunk deep, more or less rhombic, the dorsal and ventral margin 
being angulated or sharply rounded. Facial contour of head steep, 
with no marked prominence above or in advance of the orbits; 
margins of jaws with minute styliform teeth, tubercular within. 
Pin-rays closely articulated and distally bifurcating ; fulcra small 
or absent. Pectoral fins small, interiorly placed ; pelvic fins much 
smaller and remote. Dorsal fin arising about the middle point of 
the back, much elongated, high and acuminate in front, low and 
fringe-like in the posterior two-thirds ; anal fin similar in form, 
somewhat shorter, but terminating at the same point posteriorly ; 
caudal fin deeply cleft, nearly equilobate. Scales ornamented with 
more or less vertical striations, with smooth hinder border, and 
narrow overlapped anterior border; principal flank-scales very deep 
