opr 



PEGTEIT (ASQUIPSOTEIO OOrOILTIIATUS n. sp. 



Description .- Shell of mec'-itim size, slir'-htlj" ineqiailateraJ ; 

 left valve moderately' conve?:; dorsal margins converging at an 

 angle of slightly more than 90°, the posterior dorsal marfrin heing 

 longer. than the anterior, caneing a slig-ht prodiiction -oosteriorly ; 

 exterior surface sculptured v/ith seventeen strong, almost flat-top- 

 ped, hut rounded, radial ribs, separate:^ hj? interspaces of virtually 

 the same width; concentric sculpture of relatively cor spicuoias, 

 fine, sharply raised concentric lines, overriding the rios e: cept 

 in the distal half of the shell, ^he lines "being arched in the in- 

 terspaces with the oorvfiT pi'^e tnvr-'^rd the ventral margin; siihmar- 

 gins sculptured \"ith co::. centric lir-es, finer than those on the 

 ^isk; auricles suhequal, with radial and concentric sculpture; car- 

 dinal crura prominent; right valve not "i-nov^Ti. 



i^i tensions .- left valve: lat., 14,5 mm.; alt., 14,7 mm.; 

 diam., 2.S ram.; length of hing-e,. 7.5 mmC?). 



Her-'gr>s .- This sharply defiDP^ p^ecies is reioresented in 

 the material at hand hy a single left valve, She strong, subroimd- 

 ed radial ribs and, above all, the conspicuous, raised concentric 

 lines over the entire surface of t>e ^Ji bV, except on thi distal 

 portions of the rib.T, serve to distingixish this form from the assoc- 

 iated .'.e^uipectcns. *. c j .centric lines are actually closely 



