70 PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 78 



mis, but later referred by him to Indiana. In this new genus the cara- 

 pace, instead of consisting of two valves, is composed of a single plate 

 folded in such a manner that only perfect specimens are readily 

 distinguished from Indiana. 



For a discussion of the relations of Indiana to Walcottella and Diely- 

 mella, see the remarks under the descriptions of those genera. 



INDIANA UPPA Matthew 



Plate 9, Figures 1-4 



Indiana lippa Matthew, Canadian Rec. Sci., vol. 8, 1902, p. 463, pi. 2, figs. 

 lOa-lOc^; Geol. Surv. Canada, Rep. Cambrian Rocks Cape Breton, 1903, 

 p. 171, pi. 13, figs. lOa-lOd. 



Description. — Carapace subovate, widest posteriorly, hinge sHghtly 

 exceeding half of the greatest length, cardinal angles obtuse but 

 definite, anterior margin rounded, ventral margin broadly convex, 

 posterior outUne strongly convex in lower two-thirds, straight in 

 upper third to the dorsal angle. Valves moderately convex, sUghtly 

 depressed in the antero-dorsal region; with a broad, obscurely defined 

 ventral border turned inward at the extreme edge. Test very thin, 

 black and shiny in the dark matrix, minutely punctate. 



Dimensions of the best and most typical of the National Museum's 

 specimens: Greatest length 5.2 mm., length of hinge line 2.8 mm., 

 greatest height 3.1 mm., thickness about 2.7 mm. 



Remarks. — The original types of this species consist of a complete 

 carapace and the cavity from which it w^as removed. Four specimens, 

 one precisely'' hke Matthew's type, the other less confidently referred, 

 were detected in the Walcott collections. Judging from all these 

 specimens, the species occupies an intermediate position between 7. 

 secunda, I. pyrijormis, and /. dermatoides, on the one hand, and /. 

 acadica and /. primaeva on the other. In the first three species the 

 posterior half is proportionally wider, and hence the ventral edge more 

 oblique; in the latter two, the two ends of the valves are less unequal 

 and the ventral and dorsal sides of the outline therefore more nearly 

 parallel. The anterior end being rounded as in 7. secunda and 7. 

 pyrijormis, the present species is thought to be more closely allied 

 to these than to 7. dermatoides and 7. primaeva, in which the antero- 

 dorsal angle is more prominent and the upper part of the anterior 

 outhne nearly vertical. 



The contour of the valves is rather strongly convex in all of these 

 species and the surface markings, consisting of minute, widely sep- 

 arated punctae, are not materially different. An obscure umbonal 

 angulation extending obUquely backward from the antero-dorsal angle 

 is perhaps a more prominent feature in 7. lippa than in the others. 



