PLATYSOifATIDJE. 
549 
fin about one-sixth part shorterboth these fins relatively low. 
Scales resembling those of P. pcirvulus , but the striae somewhat 
finer. 
Form. Sj' Log. Lower Coal-Measures (Dalemoor Rake Ironstone) ; 
Stanton-by-Dale, Derbyshire. 
Not represented in the Collection. 
Platysomus rotundus, Hancock & Atthey. 
1872. Platysomus rotundus, Hancock & Atthey, Ann. Mag. Nat. Hist. 
4] vol. ix. p. 252, pi. xvii. fig. 2 (reprinted in Nat. Hist. Trans. 
Northumb. & Durham, vol. iv. p. 411, pi. xv. fig. 2). 
Type. Fish ; Newcastle-upon-Tyne Museum. 
A very small species, attaining a length of about 0‘075. Greatest 
depth of trunk much exceeding its length from the pectoral arch to 
the base of the caudal fin ; dorsal and ventral margins regularly 
rounded and deeply convex, thus imparting to the fish a circular 
form in side view. Several of the head-bones tuberculated; teeth 
minute. Dorsal and anal fins arising near the middle of the trunk, 
of moderate height, acuminate in front, and terminating in advance 
of the caudal pedicle: the fin-rays with distant articulations. 
Scales relatively narrower than in P. pcirvulus, and more finely 
striated. (Hancock Sf Atthey.) 
Form. § Loc. Coal-Measures: Newsham, Northumberland. 
Not represented in the Collection. 
Platysomus superbus, Traquair. 
1881. Platysomus superbus, R. H. Traquair, Trans. Roy. Soc. Edinb, 
vol. xxx. p. 58, pi. vi. 
Type. Fish; Geological Survey of Scotland, Edinburgh. 
A large species attaining a length of about 0*16. Length of 
trunk from pectoral arch to base of caudal fin scarcely more than 
three-quarters as great as its maximum depth; dorsal margin 
gibbously rounded, almost angulated at its highest point, which is 
considerably in front of the middle of the back; ventral margin 
nearly straight in its anterior half, sharply curved upwards pos¬ 
teriorly. Head with opercular apparatus occupying one-third of 
the total length of the fish to the base of the caudal fin ; length of 
cranial roof with post-temporal bone much greater than the dis¬ 
tance between the latter and the origin of the dorsal fin ; head and 
opercular bones ornamented with delicate, close, wavy, sub-parallel 
stride, occasionally passing into minute tubercles. Pelvic fins very 
