﻿TARRASIID^:. 317 



Suborder I. HAPLISTIA. 



Notochord more or less persistent. Axonosts and baseosts of 

 median fins in simple regular series, much fewer in number than 

 the dermal fin-rays. 



Only one specialized family is provisionally placed here, that 

 of the Tarrasiidaa. 



Family TARRASIID^. 



Membrane-bones of head and opercular fold well developed. 

 Pectoral fins obtusely lobate ; tail diphy cereal, with a continuous 

 dorso-caudal fin; median fin-supports more numerous than the 

 vertebral arches. 



The pelvic fins remain unknown. 



Genus TARRASIUS, Traquair. 

 [Trans. Roy. Soc. Edinb. vol. xxx. 1881, p. 61.] 



Trunk elongated, laterally compressed ; head small, its external 

 bones superficially coated with ganoine. Anal fin continuous with 

 the caudal. Caudal region enveloped in very small, thick, quad- 

 rangular, ganoid scales, which scarcely overlap but are closely 

 arranged. 



Tarrasius problematicus, Traquair. 



1881. Tarrasius problematicus, R. H. Traquair, he. cit. p. 62, pi. iv. 



figs. 4-6. 

 1890. Tarrasius problematicus, R. H. Traquair, Ann. Mag. Nat. Hist. 



[6] vol. vi. p. 494. 



Type. Imperfect fishes; Geological Survey of Scotland, Edin- 

 burgh. 



The type species, of small size, attaining a maximum length of 

 about 0*06, in which the head with opercular apparatus is contained 

 from five to six times. Scales superficially marked with a median 

 depression. 



Form. 4" Loc. Calciferous Sandstones (Cement-stone Group) : 

 Giencartholm, Eskdale, Dumfriesshire. 



P. 4704 Two fragmentary specimens, one being in counterpart. 



Purchased, 1883. 



