MONOGRAPH OF THE ATLANTIDAE. 



15 



II. Shells of 3 — 4 ram. Like the foregoing, but keel 

 extending somewhat further and reaching the inner lip, 

 sometimes even penetrating between this lip and penul- 

 timate whorl. 



III. Shells of 5 — 10 mra. With advancing age the keel 

 penetrates further between the whorls and the whole penul- 

 timate whorl may be (in the largest specimens) embraced 

 by the keel (figured by Vayssière, PI. VI, fig. 80), but 

 inner lip always in close contact with it; at the under 

 side of the shells three whorls may be seen. This stage 

 is the typical peroni- form. 



As has been said above, the spires of A. rosea and A. 

 peroni are wholly identical. Another proof that A. rosea 

 is nothing but the young stage of A. peroni is afforded 

 by the radulae. Vayssière (p. 50, PI. VI, figs. 88 and 89) 

 described and figured the radula of A. peroni and I can 

 affirm his assertions after repeated investigation. With this 

 radula the same organ in A. rosea agrees entirely. The 

 intermediate plate exhibits at its lateral side a very distinct 

 tooth, together with the usual point of this plate, but much 

 smaller; the lateral teeth are much shorter. 



The shell is wholly colourless, with exception of a faint 

 brown colour at the base of the keel, which occasionally 

 occurs. Neither is any sculpture to be seen, only a few 

 striae of growth. A good description is given by Vayssière 

 (pp. 50 and 51). 



The specimens of the Siboga-Expedition, which I have 

 formerly referred to >A. rosea 1 (p. 57, PI. VIII, figs. 22—24) 

 really do not belong to this species, but to A. depressa 

 Souleyet (see p. 21). With the information I am fortunate 

 enough to have acquired after examination of Souleyet's 

 types, I readily apologize for my error. 



Species 2. Atlanta steindachneri Oberwimmer. 



1898. Atlanta steindachneri Oberwimraer. 

 For description and figures I refer to Oberwimraer (copied 

 by me in my monograph, p. 12, PI. II, figs. 50 and 51). 



IN"otes from the Leyden Museum, A^ol. XXX. 



