426 Lt.-Ool. H. H. Godwin-Austen on 



Lead. Branchial membrane much mottled with black. The 

 animal in its characters is similar to that of E. leucostyla. 

 The generative organs (fig. B) are precisely the same, the 

 very long flagcllum (Jl.) included. 



The jaw and radula are similar, the only difference lying 

 in the formula, this being 



15+ . 1 . 12 . 1 . 12 . 1 . 15 + 

 + 28 . 1 . 28 + 



The outermost laterals were lost when removing the radula. 

 The species from the islands of the Mascarene group 

 examined by Semper and described in his ' Reisen im Archi- 

 pel der Philippinen/ p. 39, are ccelatura, Fer., and rufa, 

 Lesson, both from Bourbon. The generative organs of these 

 are figured on plate iii. figs. 22 & 23. In every respect 

 they are like those of the Mauritian species now under 

 review, with this exception, that the flagellum and sperma- 

 theca of the Bourbon species arc both shorter ; but this slight 

 departure is not, I consider, sufficient to separate them 

 generically. Semper placed them in Albers's genus Rotula, 

 of which Albers made detecta the type — a Bourbon species : 

 this I have not been able to obtain and see what the animal 

 is like, but, in all probability, it will turn out to be like 

 ccelatura, &c. * Semper also places in Rotula two other 

 species from widely separated localities, viz. : the first, 

 R. massoni, Behn, from the Andaman Islands, which, from a 

 single specimen 1 have examined, appears to be more closely 

 allied to Macrochlamys : the second is R. campbelli, Gray, 

 from Philipp Island, near Melbourne ; the generative 

 organs of this species do not accord with those of Rotula 

 rufa. I therefore come to the conclusion that the genus 

 Rotu a can only be considered a subgenus of Erepta, based 

 on its shell-chaiacter, which is very distinctive and is well 

 described, by Albers: " Teste impeiforata, lenticularis, late 

 carinala, costulate striata; anfractibus 5£, convexi, suturse 

 appressi, ultimus ba>i convexus ; apertura securiformis ; 

 peristoma simplex, margine ba-ali vix incrassato." Erepta, 

 created many years previously, must be adopted for these 

 shells from Bourbon and Mauritius. Erepta may possibly 

 be found in the Comoro Islands as well, while it will be very 

 interesting to discover if it extends to Madagascar or South 

 Africa. 



* This species detecta I have received, since these pages were in type, 

 from Mr. Ponsonby. The generative organs in all respects are similar 

 to those of Erepta rufozonata, and there is every indication of the 

 spermatophore being like that figured in PI. XI. figs. 2 & 3. There is 

 no accessory organ, and the flagellum is not extremely long. 



