24 



MONOGRAPH OF THE ATLANTIDAE. 



Shell always coloured, yellowish or brownish, especially 

 on the spire; whorls much rounded in transverse section; 

 keel extending to outer lip. 



Species 9. Atlanta turriculata d'Orbigny. 



1836. Atlanta turriculata d'Orbigny. 

 1852. Atlanta involuta? Souleyet. 



(Plates 3 and 4, figs. 25 and 26). 



Animals : 



Indian Ocean, January '06, 4 sp., Buitendijk. 



„ April '06, 5 sp., „ 



„ September '06, 1 sp., „ 



„ Movember '06, 1 sp., „ 



Gulf of Bengal, August '06, 1 sp., „ 



Spire small, forming an elevated, slender cone (tig. 26), 

 last whorl very large (fig. 25), much swollen ; aperture 

 rounded, with a small slit in the outer lip. Shell (5 — 6 

 whorls) always of a dark yellowish or brownish hue, 

 especially on the spire. No sculpture (except striae of 

 growth) in adult specimens (1,5 — 2 mm.), but in young 

 ones the shell is adorned throughout by a few very distinct 

 spiral lines; moreover, in these young specimens the spire 

 (though consisting of the same characteristic coils, rapidly 

 descending like those of Turritella) projects considerably 

 beyond the last whorl, which is much smaller than in 

 full-grown shells; the whole shell is transparent, only faintly 

 tinted with rose. 



As 1 have pointed out in my monograph (p. 58), the 

 spire is very slightly reflexed backwards ; in young shells 

 of about 0,5 mm. (as above described) it is straight. 



A. involuta Souleyet was not represented in the collection 

 of the Paris Museum. The side view of this species (copied 

 in my monograph, PI. I, fig. 18) is very much like that 

 of A. turriculata (only there seem to be more whorls in 

 the spire, though Souleyet did not mention more than 6. 



Notes from the Leyden Museum, Vol. XXX. 



