CR USTA CEA—MALA COSTRA CA . 



373 



Literature. 

 1882-83. Clarke, J. M. A. J. S. (3), 23, 25 (Devonic). 

 1884. Beecher, C. E. 2d Geol. Surv. Pa., Rep. PPP (Devonic). 

 1888. Hall, James, and Clarke, J. M. Pal. N. Y., Vol. 7 (De- 

 vonic). 



I. Stenotheca Salter. 



Univalve, compressed, and transversely corrugated carapaces, 

 without suture along the dorsal margin, and without growth lines. 

 Cambric. 



These fossils have generally been placed among the Gastropods, 

 having been considered congeneric with Metoptoma rugosa Hall 

 (Helcionella rugosa G. and S.). Matthew has referred them to the 

 Crustacea recognizing the character of the shell as that of a 

 folded carapace. They appear to be most nearly related to the 

 Phyllocarida where they are placed for the present. 



I. S. abrupta Shaler and Foerste. (Fig. 1674, a-c.) Cambric. 

 Slightly curved, rapidly decreasing, with from four to nine 

 strong corrugations decreasing upwards. 



Fig. 1674. a-Cy Stenotheca abrupta: a, interior of half of the carapace, showing 

 thickened ventral margin ; b, section of this or a related type, the straight side appar- 

 ently through ventral margin ; c, exterior ; d, S. cui'virostra ; e, S. pauper ; f, S. levis, 

 all enlarged. (After Grabau. ) 



Etcheminian of eastern Massachusetts, and in boulders which 

 probably came from Newfoundland. 



2 S. curvirostra Shaler and Foerste. (Fig. 1674, d.) Cambric. 



Very gradually tapering and slightly curved ; basal margin 

 almost straight ; corrugations numerous, stronger dorsally. 



Etcheminian of eastern JMassachusetts, and probably Newfound- 

 land. 



