ART. 4 CAMBRIAN CONCHOSTRACA — ULRICH AND BASSLER 77 



outline, in the greater convexity of the ventral margin, and in its 

 non-punctate test. From the former it differs further in the pro- 

 portionately greater height and hence in its more broadly rounded 

 posterior end. Its average size, finally, is somewhat greater. It is 

 considerably smaller than the average for I. dermatoides , has a 

 relatively longer hinge line, and is less produced posteriorly. In its 

 departure from these two species, /. matthewi approaches /. primaeva 

 (Matthew), which see for comparisons. 



Occurrence. — Middle Cambrian (Acadian-Paradoxides zone Clc), 

 Hastings Cove, Kennebecasis River, 6 miles east of St. John, New 

 Brunswick (2s) (holotype); one specimen from the Hanfordian, upper 

 part of Cl63 of Matthew's Protolenus zone, at Hanford Brook, 

 St. John County, New Brunswick. 



Holotype.— Cat. No. 50555, U.S.N.M. 



INDIANA PRIMAEVA (Matthew) 



Plate 9, Figures 9, 10 



Leperditia {?) primaeva Matthew, Trans. New York Acad. Sci., vol. 14, 1895, 

 p. 138, pi. 8, figs. 6a, h. 



A good right valve and two left valves in the collections of the 

 National Museum agree in all respects save size too closely with 

 Matthew's description and figure of Leperditia? primaeva to justify 

 specific separation. His type is from Hanford Brook, where it 

 occurred in the lower part of assize 3 of Matthew's section. Un- 

 fortunately it was not included in the collection of types loaned by 

 the Toronto University. The specimens in the United States Na- 

 tional Museum were collected by Walcott at Hastings Cove from 

 apparently the same general horizon as assize 3 of the Hanford 

 Brook section. They belong to an unquestionable species of Indiana 

 as here revised, but without seeing Matthew's figured type of L.f 

 primaeva, hesitancy is felt in stating positively that it belongs to the 

 same genus and species, although the inclination to this belief is 

 strong. Taking the characters chiefly from the specimens in hand, 

 /. primaeva may be briefly described as follows: 



Description. — Carapace subovate, relatively shorter and less 

 oblique than usual; hinge long, cardinal angles well defined, the 

 anterior and dorsal edges forming an angle of about 100°, the pos- 

 terior angle much .wider; ends unequal, though less so than in pre- 

 ceding species; lower half of the anterior outline turning backward 

 with a full curve in both valves, but the upper half varies in the two 

 valves, being nearly rectangular in the right and rounded in the 

 left; posterior margin broadly rounded below, nearly straight in the 

 upper third in the right and straight or even a trifle concave in the 

 left; ventral outline rather strongly convex, ascending somewhat 

 faster toward the front. Valves strongly convex, without nodes, 

 but showing an ill-defined yet in certain lights not inconspicuous 



