onl^- irrecrviiarlj- ST'Scecl inorementals ; -.-'> ^ " ^-f-'r,.- from f'^^^ .--^o 

 over the disk numerous verv obscure rat^ial elevations arid wider' 

 depressions of varj'ing width, occasionally entirel;^ absent; hing-e 

 •"*i;> one right and two left vardinals; inner margin of the valve 

 finely ereniilaterl. 



Dimen.- ioiia .- lat., 16.5 mm.; alt., 16.5 mrn. ; semidiam. , 

 S.n mm.' 



Remarks .- 'Ihis is one of the most abundant of the lueinidae. 

 The largest individual has the following dimensions: lat., 18.5 

 mm.; alt., 18 mm.; semidiam., 4.6 mm. The diagnostic feat^jres 

 are the obscure radials, the fine concentric rugae, which become 

 slightly raised and sharp toward the margins, both vent rally and 

 on the dorsal areas, and the c renulatioiis on the inner margin. 'I'he 

 radials are always weak, but occasionally they are sufficiently 

 emphasized to cause the edge of the ventral concentric ru„gae t5 

 be slightly unrlulated. In addition to these relatively coarse 

 radials, very fine and obscure radial lines may be present on 

 the me'iian portion of adult shells. 



Yoimg valves which have the radials obsolete and ■■■'^'-' concen- 

 tric sculpture emphasized may be confused with the associate'' 

 i:yrtaea limoniana of the same' size' and this resemblance is aug- 



rjsnted by the similarity of the "uij.ige. In general the ^jruaent 

 form is slightly more convex, with more prominent nmbones and a 



