68 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 7 



tinctive features of the species. These two ventral nodes probably 

 represent the submarginal folds of P. marginata, while the tubercle 

 just above the anterior one of the two is regarded as corresponding to 

 the principal node in P. angelini and P. marginata. The dimensions 

 as given by Gronwall are as follows: Length 3.0 mm., height 1.4 mm. 

 Occurrence. — Middle Cambrian, Davidis zone, near Borregaard, 

 Bornholm, Denmark. 



Family INDIANIDAE new family 



Small oval bivalved Conchostraca with surface of valves even, 

 smooth, and not exhibiting an ocular tubercle. Valves open along 

 the anterior and posterior ends and widely gaping along the ventral 

 edge. Shell structure corneo-calcareous, polished. 



Genus INDIANA Matthew (emended) 



Indiana Matthew (part), Canadian Rec. Sci., vol. 8, 1902, p. 460; Geol. Surv. 



Canada, Rep. Cambrian Rocks Cape Breton, 1903, p. 169. 

 Not Indiana Jones, Geol. Mag., Dec. 4, vol. 9, 1902, p. 402. 



Carapace bivalved, rather small, 4 to 7 mm. long, the outline a 

 more or less obliquely truncated ellipse, the hinge being straight but 

 of varying length and sharpness of definition. Anterior extremity 

 commonly bowed forward from the antero-dorsal angle, at other 

 times descending vertically from the angle. Postcardinal angle 

 obtuse, occasionally rounded off, more commonly distinct. Posterior 

 margin broader than the anterior, sometimes following a regular 

 elliptic curve, oftener obliquely truncated or even slightly concave 

 in the upper part. Valves rather strongly convex, usually somewhat 

 depressed in the anterior half of the dorsal slope; without nodes. 

 Free edges of valves with or without a delicate external rim, occa- 

 sionally expanding into a wide, flattened border sometimes developed 

 only on the anterior end ; inner side of edge bent inward. Gap between 

 edges of opposite valves widest at the ends, chiefly made up by con- 

 cavity of the ends of the left valve. Test thin, black to brown or 

 yellow, polished, minutely punctate, somewhat pliable chitinous, 

 including very little calcareous matter in its composition. 



Genotype.— Indiana lippa Matthew (selected by the writers). 



Remarks. — In the original description of Indiana by Matthew ^ no 

 genotype was designated. The first species following the generic 

 diagnosis is /. ovalis, and this species, under the rules generally pre- 

 vailing in such cases, has been cited as the genotype. Unfortunately, 

 as has been already mentioned in discussing Bradoria, the genus can 

 not be maintained if founded on /. ovalis. The imperfect original 

 tj'pe of this species, after careful comparison, >vas positively identified 



*> Canadian Rec. Sci., vol. 8, 19U2, p. 4tjO. 



