MONOGRAPH OF THE ATI.ANTIDAE. 



only to an experienced eye. It will be more advisable to 

 refer to the figures. 



Species 1. Atlanta peroni Lesueur. 



1817. Atlanta peroni Lesueur. 



1832. ,, keraudreni Quoy et Gaimard. 



1840. costae Pirajno. 



1852. ,, kero.udreni Souleyet. 



1852. ,, rosea Souleyet, non Tesch (1906). 



1883. Oxy gyrus keraudreni Ray Lankester (copied by 



Pelseneer in Treatise of Zoology, Mollusca, fig. 141, 



p. 161, 1906). 



(Plates 1 and 2, figs. 7—9). 



Dry shells : 



Atlantic Ocean, purchased 1907, 15 sp., Sowerby and Fulton. 

 Animals : 



Red Sea, March 16, '07, 2 sp., Buitendijk. 



Gulf of Aden, August '06, 1 sp., „ 



Indian Ocean, April '0G, 1 sp., „ 



As is well known, the keel penetrates to a great extent 

 between the whorls, but this character is only pronounced 

 in adult specimens. The young shells, of which the material 

 collected by Mr. Buitendijk consists, belong to the form 

 rosea, which has been regarded by Souleyet as a distinct 

 species. I have carefully examined shells of all ages, and 

 after becoming convinced that the spires of A. rosea and 

 A. peroni are absolutely identical (as is also the case with 

 the characteristic radula), I may be allowed to give the 

 following series: 



I. Shells of 0,5 — 2 mm. (figs. 7—9). Rosea-tovw. Keel 

 not reaching inner lip of aperture, faintly tinted in brown 

 at the base ; spire 'somewhat projecting (fig. 8) ; at the 

 underside of the shell more than two whorls are visible 

 (fig- 9). 



Notes from the Leyden Museum, "Vol. XXX. 



