356 



NORTH AMERICAN INDEX FOSSILS. 



73. K. marginalis Ulrich and Bassler. (Fig. 1663,1.) Devonic. 

 Similar to K. manliensis, but more elongate, with wider margin, 



shallower sulci, and smooth surface. 

 Helderbergian ( ?) of New Brunswick. 



74. K. centricornis Ulrich and Bassler. (Fig. 1663,;.) Devonic. 

 Valves more elongate than other species, median lobe spine-like ; 



surface coarsely pitted. 



Coeymans limestone of Cumberland, Maryland. 



75. K. fimbriata Ulrich and Bassler. (Fig. 1663, ^.) Devonic. 

 Median lobe with constrictions, margin spinous, surface pitted. 

 Coeymans limestone of New York. 



XXXI. ScoFiELDiA Ulrich and Bassler. 

 Carapace 2 to 3 mm. long, oblong, subquadrate, compressed; a 

 small median node around which other nodes and ridges are 

 arranged symmetrically. 'One species. Ordovicic. 



Fig. 1664. a-c, Drepanella macra (43), right valve, with longitudinal and vertical 

 sections through center of valve ; d-f, Scofieldia bilateralis (76): d^ right valvg; <f,/, 

 ventral and posterior views of a left valve, all X ^o. (After Ulrich.) 



76. S. bilateralis Ulrich. (Fig. 1664, J-/.) Ordovicic. 



With a large irregular triangular and ridged node on each side 

 of the small subspinous median node, and a broad curved ridge 

 along ventral margin. (Type of genus.) 



Trenton of Minnesota. 



XXXII. Treposella Ulrich and Bassler. 



Carapace small, about i mm. long, semiovate to subquadrate; 

 carved free margins, with radiately striated frill; ventral margin 

 swollen, forming a low ridge in right, and an elongate ventral 

 node ("pouch") in the left valve; a rounded posterior and elon- 

 gate anterior node occur above this. Devonic. 

 yy. T. lyoni (Ulrich). (Fig. 1665,1-^.) Devonic. 



Posterior node round, anterior balloon-shaped, projecting above 



