TARRASIIDiE. 
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 Tarrasiidae. 
Family TARRASIIDiE. 
Membrane-bones of bead and opercular fold well developed. 
Pectoral fins obtusely lobate; tail diphycercal, with a continuous 
dorso-caudal fin; median fin-supports more numerous than the 
vertebral arches. 
The pelvic fins remain unknown. 
Genus TARRASIUS, Traquair. 
[Trans. Iioy. Soc. Ediub. 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. Sf Log. Calciferous Sandstones (Cement-stone Group): 
Giencartholm, Eskdale, Dumfriesshire. 
P, 4704 Two fragmentary specimens, one being in counterpart. 
Purchased, 1883. 
