from the Province of Tavoij. Aoo 



whorls six, flattened above, and separated by an indistinct, 

 margined suture ; periphery prominently and acutely carinate, 

 above regularly and closely costate-striate ; beneath convex, 

 with very minute striae of growth, smooth and shining ; cen- 

 trally-excavated, and with an almost imperceptible umbilicus ; 

 aperture commencing a little below the carina, lunate, with a 

 sinus or angle where the keel terminates; lip simple, sharp. 



Diameter y^ of an inch ; height less than | of an inch. 



In general form, color, and sculpture, it resembles H. acies, 

 Fer., (acutimargo Rosm.) but is much smaller, and not widely 

 umbilicated. 



HELIX (Caracolla) RETRORSA. 



Plate XXIV. Fig 5. 



Tesla orbiculata, sinistrorsa, utrinque convexa, pallide castanea, arete umbilicata ; 

 anfr. 5, lineis longitudinalibus et volventibus minute rugosis, ultimo cariuato ; aper- 

 tura rotuuriata, labro acuto. 



Description. 



Shell large, sinistral, orbicular, about equally convex above 

 and below, but most rounded below ; of a pale chestnut or 

 fawn-color above, growing paler to the umbilicus, where it is 

 pale horn-color. Surface somewhat undulated by the irregu- 

 lar lines of growth, and rendered minutely rugose by very 

 fine, serpentine, revolving lines, forming conspicuous wrinkles 

 near the carina ; whorls five, forming a regular, moderately 

 elevated spire, the suture slightly impressed, the periphery 

 surrounded by a prominent, compressed, but acute keel, which 

 becomes lost towards the aperture ; aperture rounded, height 

 and width about equal ; lip simple, slightly everted in the 

 umbilical region : some vitreous matter across the penultimate 

 whorl ; umbilicus rather large, but not deep. 



Diameter 1| inches; height 1 inch. 



This large heterostrophe Helix resembles an inverted spe- 

 cimen of one of that group of shells, so common and so 

 varied, from the Philippine Islands, of which H. Lamarckii 

 is one. Young specimens might, at first glance, be con- 

 founded with H. Himalana, Lea; but the Himnlana is much 

 more globular, the surface less striated, the carina quite indis- 

 tinct, and the umbilicus smaller. 



