1336 SPATITA 



boid. It is a very Httle higher at the place where the base is 

 full than in front. The substance is thin, the epidermis yel- 

 lowish or tawny-green ; nacre lurid purple. Lea's modesta 

 is more slender than these shells and has a bluish nacre, von 

 Martens' 5. pctcrsi as figured seems to stand between the. two 

 lots. 



Spatiia arcuata (Cailliaud). 



Shell somewhat elongate, subrhomboid and arcuate, convex 

 to subinflated. solid, inequilateral ; beaks but slightly elevated, 

 apparently having oblique sculpture ; dorsal and posterior out- 

 lines curved, sometimes subangulate behind "the ligament ; an- 

 terior end rounded ; base decidedly incurved ; posterior ridge 

 rounded ; there are sometimes one or two low, radial ridges 

 above it ; surface with irregular, concentric striae ; epidermis 

 dull, greenish or greenish-brown ; left valve with a compressed 

 rudimentary tooth, which fits into a corresponding depression 

 in the right valve ; muscle scars impressed ; dorsal scars deep ; 

 nacre whitish or flesh-colored, pearly. 



Length 82, height 47, diam. 34 mm. 



Length 90, height 48, diam. 31 mm. 



Length 80, height 38, diam. 24 mm. 



Egypt ; Abyssinia. 

 Anodonta arcuata Caiijjaud, Voy. a Meroe, IV, 1826, p. 263 ; 



II, pi. i.x, figs. 4, 5. — PClkssin, Conch. Cab. Ano., 1874, p. 



145, pi. xi<vii, figs. I, 2. 

 Margarita (Anodonta) arcuata Le.-\, Syn., 1836, p. 54; 1838, p. 



32- 

 Iridina arcuata Pm iez and Michaud, Gall. Moll., 1844, P- 146, 



pi. LV, fig. 4. 

 Mar^aron (Anodonta) arcuata Lea, Svn., 1852, p. 53; 1870, 



p. 83. 

 Spatha arcuata Jickklt, L. and S. Moll. N. Ost-Af., 1874, p. 



265. — Simpson, Syn., 1900, p. 899. 



It will be seen by the above measurements that this species 

 is quite variable in size. It has a heavy shell with a decidedly 

 arcuate subrhomboid outline, greenish or greenish-brown epi- 

 dermis and whitish or silvers nacre. 



