72 



Bulletin 39 



244 



ly thickened outer lip; canal short, slightly bent inward or out- 

 wards; callous on the inner lip. 



Length 20, diameter 7.5, last whorl 11 mm. 



The general form of this shell is that of Drillia venusta Sow- 

 erb}^, which it also recalls in its constricted anal fasciole. The 

 whole surface appears minutely shagreened, an effect produced by 

 the fine, sub-microscopic, spiral threads as well as a minute de- 

 cussation of their interspace. This species is fairly abundant in 

 certain sand}^ layers found intercalated in the hard and gener- 

 ally barren coral-reef limestone along the sea-front at Port 

 Limon. 



Gatu7i Stage: Port Limon. 



Drillia Cristobali, n. sp. Plate 5, figure i 



Shell of the general form of uenusta, rather solid; whorls 6, 

 (apex broken in the type specimen); anal fasciole a narrow con- 

 stricted zone, bordering the upper suture; no sutural cord; sculp- 

 ture of numerous, straight, parallel ribs and fine spirals; ribs on 

 the early whorls about 12, becoming about 19 on the last; on the 

 anal fasciole, the ribs are shortly deflected or bent; spirals very 

 numerous and on slight magnification seen to consist of narrow, 

 even raised threads with interspaces of nearl}^ twice the width of 

 the spirals themselves; anterior canal rather short and slightly 

 bent backwards; aperture sub-ellipitical with a thin outer lip; 

 anal sinus small and shallow. 



Length 20, diameter 8.5, last whorl 11.5 mm. 



This species, like the limo?iensis, has the general form and 

 constricted fasciole of Drillia veniista Sowerby, but differs by its 

 smaller size, short canal and quite different spiral and axial 

 sculpture. D. limonensis, is more closely related, but that 

 species differs in its more slender form and peculiar submicro- 

 scopic sculpture. 



The single specimen serving as the t5^pe, was collected 

 from the Gatun shale, exposed about a mile north of the city 

 of Bocas del Toro, on Columbus or Cristobal Island. 



