﻿22 



MONOCnAPH OF THE ATLANTIDAE. 



2°. by the deeper fissure in the outer lip, 3°. by the umbilicus, 

 the three last whorls (in A. inflata only two) being visible 

 at the under side of the shell (fig. 20), and 4°. by the absence 

 of colour on the spire. Besides, the spiral sculpture is so 

 slightly pronounced, that even in young shells and with 

 great magnificent power, scarcely any trace of it is to be 

 found. The side views of A. inflata (fig. I4j and of A. 

 depressa (fig. 19) differ also in the fact, that in the first 

 species the aperture is much larger, and that the spire is 

 a regular, short cone, whereas in A. (ieprma it is somewhat 

 irregular, the first two whorls forming a higher, more 

 elevated cup. 



I have figured also a specimen (figs. 21 and 22), which I 

 regard, though hesitatingly, as A. depressa. The shell, seen 

 from apex, with its few whorls, resembles A. lesueuri^), 

 especially on account of numerous curved lines of growth, 

 occurring on the last whorl (fig. 21); the side view on 

 the other hand (fig. 22) is most like that of A. depressa. 

 Near the aperture the shell was seriously damaged. 



I greatly regret to confess that I have been mistaken 

 in my monograph, in designating the true A. depressa of 

 the Siboga-Expedition to A. rosea (p. 57, PI. VIII, figs. 

 22 and 23). In the collection of the British Museum I had 

 at that time the opportunity to examine, A. depressa was 

 not represented, and this may account (and in some 

 way apologize) for my mistake. Comparing the here given 

 figures with those formerly published, the identicalness 

 will be evident. 



Species 8. Atlanta helicinoides Souleyet. 



1852. Atlanta helicinoides Souleyet. 



1904. Atlanta quoyana Vayssiere, non Souleyet. 



(Plates 3 and 4, figs. 23 and 24). 



Animals : 



Red Sea, January '06, 1 sp., Buitendijk. 



1) Here, however, the spire is much smaller in proportion to the last whorl 

 Notes from the Leyden Museiim, Vol. XXX. 



