i6 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



L.BELLAPLICATA 

 NOVAMEXICANA 



L.BELLAPLICATA 

 BELLAPLiCATA 



L.LUGUBRIS 



NOVAMEXICANA 



Fig. 5. — Evolution in the Lopha lugubris group. A, B, C, Drawings and cross 

 sections of characteristic cardinal areas for species and subspecies within the 

 group. Note gradual deepening, and increase in curvature of the resilifer in 

 progressively younger forms. Also note increase in convexity of the lateral 

 cardinal areas, from slightly arched lateral cardinal plates in the subspecies 

 novamexicana, to distinct lateral cardinal folds in L. higubris. D, Outline 

 drawings of species and subspecies within the group, with the auricular sulci 

 shaded. Note narrowing of the sulci in progressively younger forms, and varia- 

 tion in shape of the valves, of the posterior auricle, and in development of the 

 anterior auricle. Specimens: A, U.S.N.M. 132263; B, U.S.N.M. 132243; 

 C, U.S.N.M. 132167; D. Top row, left to right, U.S.N.M. 13274, 132154, 

 U.M.M.P. 43472, 43464, U.S.N.M. 132157; middle row, left to right, U.S.N.M. 

 132229, 132225, 132308; bottom row, left to right, U.S.N.M. 132263, 132267, 

 132281, 132279. 



