more delicate. The soiilpture is p.iinutely safj-ririate, tlie lerifth 

 10. ^, ^-he diev-pt.-r s.^oovt "■ '^-i ■-." (i^n1l, ^^ j). 



■J^'Pe loocJ-i':: .- 3ov./deri, lea. 



Shell small, thin, subtranslucent , moderatel^r inflated, 

 transvc-"''"'='T- eloii^?'^'^'"i ^ '-•r-i^f.p-^ ' " " , ; - •^o:.v-,_.t-vc-3-i , o p_ 



gin short', slino3t straight, roimdirjg oroadl^- into the lorig ob- 

 licuel; siihtruncated postero-lateral inar^-in, vhich ahniptlj 

 roiondG into the base; -■---e attenuated ^ -^o^\-r.^'e^^- -^-"teriorl^, 

 b--.ss gentl;/ arcuate, deccending to\7ard the posterior end; -ambo 

 low, place" -:rd the anterior end, at the sar-e elc/ation as 



the highest -"--^ -^^ ';;.•,- ^-u-- o .r'^ -^"^ Tiargir. , ■■ng from the imbo 



to the postero-ventral angle as a rounded keel, flattened toward 

 the margin; near the margins the surface of the shell ^vith relative- 

 ly; coarse grannlationo ; hj '" subumbor. " ""^inal". 



Dir.'.ensioris .- Length, 5 mm.; e."!"'"., " nm. ; semidiam. , 1.5 mn\. 



Remarks .-- This species is re^iresented b;; an incomplete, 

 small left valve, ■.'t'hen compared . Li-i- ''"■ — this valve shprs 



certain differences that probably are due to immaturity j it is 

 m.ore definitely kelled, v/ith a louver umbo, ;ore obviously and 



coarsely graniilose surface. Other features that are iiot in common 

 are due to the differences betv:een right and left valves; the 

 edge of the postero-dorsal mar~in of the right valve is flexed to- 

 v/ard the interior of the ahell, v.hile on the left valve it flar-L- 

 outvrard and the left tooth is directed more to the rear. 



