13^- PLEIODON 



Pliodon (Cameronia) vynckci Germain, AIoll. L. Tan., 1908, 



p. 87, figs. 49, 50, 5T. 



'"This species is principally characterized by its short, more 

 or less subtrigonal form, much developed in height, and by 

 its prominent, well-inflated, nearly central beaks. The dorsal 

 margin is distinctly curved in a direction slightly ascending; 

 anterior end rounded ; basal margin subconvex, slightly in- 

 curved in the centre ; posterior end twice as long as the ante- 

 rior and prolonged into a beak that is almost basal. The shell 

 is thick, solid, heavy, quite strongly striate ; epidermis a bril- 

 liant, deep brown ; nacre roseate, slightly bluish at the mar- 

 gins." (Germain). 



Pi.EiODON TciiADiF.NSi.s Germain. 



"Shell large, very elongate-oblong; valves moderately in- 

 flated, very thick and heavy ; dorsal margin slightly convex as 

 far as the postero-dorsal angle ; ventral margin medially in- 

 curved, nearly parallel to the dorsal margin ; anterior region 

 moderate, semi-elliptical ; posterior region well developed, 

 more than twice as long as the anterior, terminating in a short 

 point, slightly elevated ; dorsal ridge moderate, very obtuse ; 

 beaks obtuse, much compressed, not prominent, eroded, show- 

 ing a beautiful, very iridescent, bluish nacre ; muscular impres- 

 sions deep; hinge scarcely denticulated in front, strongly den- 

 ticulated posteriorly. Epidermis dark chestnut; lines of 

 growth quite strong and irregular nacre salmon-rose, re- 

 markably iridescent. 



Length 160, height 62.5 mm. at 66 mm. from the beaks, 

 diam. 39 mm." (Germain). 



Type locality, Lake Tchad. 

 Pliodon (Cameronia) tchadiensis Germain, Bull. Mus. Hist. 



Nat., 1905, p. 489 ; Ibid, 1906, p. 60, fig. 4 ; TAfrique Cent. 



Fr., 1907, p. 578, fig. 98. 



Pi,EiODON HARDELETi Germain. 



"Shell much elongated, slightly w-edge-shaped ; valves quite 

 inflated, thick and solid ; dorsal and ventral margins divergent ; 

 dorsal margin subconvex, slightly ascending ; ventral nearly 



