1882.] MOLLUSCAN FAUNA OF MADAGASCAR. 381 



united to the outer lip by a very thin granulated callosity, coating 

 the whorl within the aperture. 



Greatest diameter 76 millim., smallest 58, height (resting on its 

 base) 35. 



Hub. Ekongo, South-east Madagascar ( Waters). 



This is the species erroneously considered by Mr. Angas to be the 

 H. guestieriana of Crosse, which much more closely resembles H. 

 ibaraoensis of the former author. H. guestieriana is a more globose 

 shell, with a higher penultimate whorl, a shorter aperture, a smooth 

 columella, and a smooth callosity upon the body-whorl, which is 

 encircled by several slightly raised ridges of more equal size than in 

 H. bicingulata. The granular and slightly arched-forward columella 

 in the latter species, the obliquely indented surface of the body- 

 whorl, and the two very conspicuous brown slightly raised girdles 

 around it, the lower one bordered by an indistinct pale one above, 

 distinguish this from the allied forms, H. cornu-giganteum, H. bet- 

 sileoensis, H. ibaraoensis, and H. guestieriana. The first two are 

 openly umbilicated, the third generally imperforate (in about fifty 

 specimens I have seen a few with a narrow perforation) ; and the 

 last is said to be "narrowly subrimate." H. betsileoensis has the 

 columella granular as in the present species ; in the other three it is 

 smooth. In H. ibaraoensis the callus uniting the columella and the 

 outer lip and spreading over the whorl within the aperture is con- 

 spicuously granulated, and the epidermis is nearly black towards the 

 lip. 



All the five species here remarked upon are, no doubt, offshoots 

 from one original progenitor ; still I have found no difficulty in recog- 

 nizing any specimen which has yet been examined. Probably no two 

 exist in precisely the same locality. The following is the distribution 

 as at present known : — 



H. cornn-gigantemn. 



Hab. Island of Agalega, N.E. of Madagascar {teste Sir David 

 Barclay !). 



H. guestieriana. 



Hab. Madagascar (no precise locality known). 



H. betsileoensis. 



Hab. S.E. Betsileo {Angas) ; Tanala country {Deans Cowan), 



H. ibaraoensis, 



Hab. S.E. Betsileo {Angas) ; Tanala country {Deans Cowan). 



H. bicingulata. 



Hab. Ekongo, south-east of the island {Waters). 



Helix (Macrocyclis?) covani, Smith. (Plate XXI. figs. 

 10-12.) 



Helix {Macrocyclisl) covani. Smith, Journ. of Conch, vol. ii. 

 p. 338. 



Hab. Ankafana, Betsileo province {Cowan). 



This species was originally described from a single specimen which 



