- 17;^ - 



"alatis, pauois, sutiobsoletis : marglne valde plicato, intusque 

 ma,'?is miniisve scabro; natibus incizrvatis; superficie interna albo- 

 virescente, n-amquam mar^aritaeea; cicatrice satis magna, reniforrai. 

 Long. 5 poll." 



"A rare and extraordiioarj- species, \?hiG]a hears not the slii-^ht- 

 est resemblance to any of the recent Ostraea. '^he narrow sickle- 

 shaped contour and .Gigantic marginal tooth-like foldo form its most 

 distinctive character. '2he adult specimens are attached by their 

 apices only." (HanDey, 1845). 



Shell small, thin, sub e qui valve; both valves compressed or 

 slightly convex:; outline variable elongate and longitudinally sub- 

 ovate to subfalcate; left valve bearing three to five broad, ir- 

 regular, subangular to roui'.ded plications, most prominent at the 

 ventral mar~in and extend only a short distance from the mars-in; 

 denressions between the plications broader, t- inner and less ang- 

 ular than the plications; right valve v.-ith similar, b;it less promi- 

 nent, plications or more frequently irregularly warped; both valves 

 Tvithout definite concentric sculpture except inconspicuous, usually 

 non-laminated incremental lines; ligament area wide, oblique in pos- 

 ition, with, on the left valve, a broad, shallow median depression; 

 submargins finely, but conspicuously corrugated; muscle scar rela- 

 tively large, posterior in position, longitudinally subellintical 

 to broadly subovate in outline, with the anterior dorsal ir.ar-^in 

 deeply em.arginated. 



