﻿MICniOMDUS 



245 



muscular impressions moderate, anterior accessory impression 

 moderate, subrhomboid ; nacre violaceous red. 



Length 82, height, at beaks, 2-], at posterior end, 38 diam. 

 15 mm.'' (now Martens). 



Anodonta ( Lainproscapha) schombur^^ki von Martens, Pr. 

 Zool. Soc. Lond., i860, p. 15. 



Pilsbryoconcha schombiirgki Simi-son, Syn., 1900, p. 588. 



I know nothing of this species. Yon Martens remarks that 

 "the thin and very flat shell and the want of edges at the mar- 

 gins render it impossible to associate this species with Spatha 

 rostrata." I presume that it should be placed in Pilsbryocon- 

 cha and it is possible that it is synonymous with some one of 

 the other species here described. 



Genus MEDIONTDUS Simpson, igoo. 



Medionidus Simpson. Pr. Ac. N. Sci. Phila., 1900, p. yy.-~ 

 Ortmann, Ann. Car. Mus., VIII, 1912, p. 334. 

 Shell elongated, rather inflated, often arcuate when adult, 

 generally having a posterior ridge ; dorsal slope and occasion- 

 ally the i)osterior portion of the shell plicately or nodulously 

 wrinkled : epidermis smooth and bright, variegated with brok- 

 en green rays and blotches ; beak sculpture consisting of rather 

 fine, subparallel, often broken ridges in two loops, the anterior 

 rounded, the posterior somewhat angled, occasionally broken 

 up into zigzags ; pseudocardinals small, stumpy, and somewhat 

 roughened : laterals rather short, slightly curved and club- 

 shaped, remote ; dorsal cicatrices few, placed under the hinge 

 just behind the beaks ; anterior cicatrices rather deep; posterior 

 cicatrices rounded, large, and well impressed : anterior part of 

 shell somewhat thickened; female shell slighth' swollen just 

 behind the middle of the base. 



Animal having inner gills wholly or in part free from the 

 abdominal sac : marsupium occupying the central posterior 

 part of the outer g"ills, sometimes extending nearly their whole 

 length, consisting of few to many rather large, irregular ovi- 



