204 RIEBECKIA. 



drawn in pi. 50, fig. 39, is 97 mm. long, and Kobelt figures a 

 shell 100 mm. long. The type of C. eximius, not fully mature, 

 is 120 mm. long. 



The last whorl is rich chestnut with darker and lighter 

 streaks, preceding whorls being mainly yellow with chestnut 

 streaks. The suture is hardly impressed at first, but its. 

 depth increases to the last whorl. On the last three whorls 

 it has a distinct, crenulate margin below. The striation is 

 weak and irregular on the later whorls, and the spiral decussa- 

 tion while weak is readily visible. 



Ancey remarks that a specimen from Imerina is shorter and 

 more ventricose than others he has seen. 



9c. Var. crossei Kobelt. PL 50, figs. 40, 41. 



Shell smaller, the length about 85 mm.; spiral sculpture 

 inconspicuous. 



Clavator eximius CROSSE et FISCHER, in Grandidier, Moll. 

 Madag., pi. 22, f. 1, la. Clav. crossei or Cl. eximius var. 

 crossei KOBELT, Conchyl. Cab. p. 654, pi. 100, f. 2, 3 (copied 

 from C. & F.). 



Crosse and Fischer 's figures, copied on my plate, show faint 

 spiral striation on the penult, whorl. I consider this, like 

 C. balstoni, merely a small form of C. eximius. 



Genus RIEBECKIA v. Martens, 1883. 



Riebeckia v. MART., Conchol. Mittheilungen ii, p. 148 

 (1883), type Stenogyra sokotorana. KOBELT, Conchyl. Cab. 

 i, lOte Abth., p. 84. SMITH, in The Natural History of 

 Sokotra and Abd-el-Kuri, 1903, pp. 131-137 (monograph). 

 Balfouria CROSSE, Journ. de Conchyl. 1884, p. 356, for 

 Stenogyra hirsuta G.-A. 



Shell turrited, perforate or closed, composed of 10 to 15 

 compactly coiled whorls; pale, not variegated, vertically stri- 

 ate, decussate or smooth, rarely hairy. The two embryonic 

 whorls form a globose, obtuse summit, which is retained en- 

 tire in the adult stage. Aperture less than one-fourth the 

 total length, the outer lip simple, columella vertical or arcuate, 

 varying from distinctly truncate below to almost continuous. 



