﻿PLATTSOMATTDiE. 



549 



fin about one-sixth part snorter ; both these fins relatively low. 

 Scales resembling those of P. parvulus, but the striae somewhat 

 finer. 



Form. $ Loc. Lower Coal-Measures (I)alemoor 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. parvulus, and more finely 

 striated. {Hancock Sf AttJiey.) 



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. Pish ; Geological Survey of Scotland, Edinburgh. 



A large species attaining a length of about 046. 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 

 striae, occasionally passing into minute tubercles. Pelvic fins very 



