1378 PJ^EIODON 



Pliodon ovaUis var. pachyodon Gl^KMAIN, Arch. Zool. Exp. et 



Gen., (5), I, 1909, pp. 44, 59, fig. 41. 



This form from Le Bafing, Seneg-al, characterized by its ex- 

 ceedingly heavy hinge, Germain, (1. c), considers worthy of 

 varietal rank. 



Subgenus Camrronia I5ourguignat, 1879. 



Cameronia Bourcuigxat, Moll. Egypt and Ab., 1879, p. 42. 



Anterior end of the hinge plate u.sually (not always) split 

 up lengthwise into irregular teeth, which bear tubercles on 

 their surfaces. 



The mantle of P. spckii has a decided pallial sinus behind. 

 (Pelseneer.) 



Type, Iridina spckii Woodward. 



Pleiodon spekii Woodward. 



Shell elongated, solid, somewhat variable in form, long ellip- 

 tical, long ovate or slightly obovate, more or less inflated, in- 

 equilateral ; beaks full, elevated and elongated ; posterior ridge 

 rounded : dorsal outline arched ; anterior end rounded, some- 

 times narrowed and subangulate above ; base straight, curved 

 or lightly incurved medially ; posterior end usually bluntly 

 pointed ; surface nearly smooth ; epidermis dark chestnut to 

 reddish-brown, somewhat shining ; hinge "with irregular, taxo- 

 dont teeth, the anterior part having cross teeth ; muscle scars 

 well marked ; nacre whitish to violet, brilliant. 

 • Length 120, height 50, diam. 45 m. 



Length 14T, height 67, diam. 45 mm. 



Length 107, height 44. diam. 41 mm. 



Lake Tanganyika. 

 Iridina (Pleiodon) spckii Woodward, Pr. Zool. Soc. Lond., 



1859, p. 348, pi. XLVH. fig. 2. 

 Pleiodon spckii Sowerhy. Conch. Icon., XVL 1866, pi. i, fig. 2. 

 Platiris (Iridina) spekii Lea, Syn., 1870, p. ^8. 

 Cameronia spckii Bourguignat, Moll. Egypt and Ab., 1879, 



P- 43- 



