﻿MONOGRAPH Of" THE ATLANTIDAE. 



27 



cone, which is very couspicuously reflexed on the last 

 whorl (figs. 30 and 31), 2°. the keel extends for some distance 

 on the penultimate whorl, and 3°. the whole shell is colourless 

 and quite transparent, with exception of an occasional 

 diffuse brownish hue at the inner lip. Aperture rounded 

 (fig. 31), outer lip deeply fissured. 



In one of the type-specimens of Souleyet, which I have 

 figured here, a remarkable sculpture is visible on the spire 

 (fig. 30), consisting of numerous transverse striae, radiating 

 from the apex, mostly on the 2"^^, 3'^ and 4^^^ whorl. In 

 other specimens 1 have not observed this feature. The same 

 shell also exhibits (fig. 32) around the umbilicus, and 

 likewise radiating from it, a number of very fine grooves, 

 slightly undulating in their course; here the penultimate 

 whorl (as in all the specimens I have seen) is not rounded, 

 but forms an obtuse angle in transverse section (fig. 32). 

 On the last whorl transverse lines of growth are very distinct. 



Species 12. Atlanta gibbosa Souleyet. 



1852. Atlanta gibbosa Souleyet. 

 1859. Atlanta gibba Chenu. 



(Plate 5, figs. 33 and 34). 



Dry shells : 



Indian Ocean, purchased 1907, 2 sp., Sowerby and Eulton. 

 Animals : 



Buitendijk. 



Red Sea, 



April 



'06, 



1 



sp., 



Indian Ocean, 



January 



'06, 



1 



sp.. 





April 



'06, 



1 



sp., 



Gulf of Aden, 



August 



'06, 



1 



sp., 



Spire very large, more than in any other species (fig. 33), 

 reflexed forward ; last whorl comparatively small (fig. 34) ; 

 outer lip deeply fissured. A single spiral line, following 

 the suture (fig. 34). Shell colourless, entirely transparent. 



This small species resembles very much a [young stage of 



Notes from the Leyden Mizseum, Vol. XXX, 



