107 



T. orbiculari, depressa, fere planorbula, tenui, alba; 

 spira depressa, anfractibus 4, distinctis, rotundatis, spira- 

 liter sulcatis ; apertura circulari, peritremate tenuissimo, 

 acuto. 



Shell orbicular, depressed, nearly flat, thin, white, with 

 a depressed spire, consisting of four volutions, not quite 

 contiguous to each other, rounded and spirally grooved ; 

 aperture circular, with a very thin sharp-edged peritreme. 



48. C. cornu-venatorium. Gmel. (pi. xxiv. f. 41, 42.) 

 T. orbiculato-depressa, albican te; spira mucronata, nigra; 



anfractibus 4 ventricosis, superne transversim striatis, infra 

 lsevibus, linea mediana ferruginea; sutura produnda.; apertura 

 circulari, peritremate tenui, acuto ; umbilico maximo. 



Shell orbicular, depressed, whitish ; spire mucronated, 

 with a black apex ; volutions 4, ventricose, transversely 

 striated on the upper part, smooth beneath, with a brown 

 spiral line in the middle ; suture deep ; aperture circular ; 

 peritreme thin, acute ; umbilicus very large. 



Obs. This species approaches most nearly in shape to C. 

 Planorbulum Lam. ; it may, however, be distinguished by its 

 lip not being at all reflected. 



49. C. l^evigatum. (t. xxiv. f. 62, 63.) Webb et Berth- 

 elot, Ann. des Sc. Nat. Mars 1833. C. Canariense D'Orb. 



T. subrotundata, albida, fulvo-fasciata, leevi, spira acumi- 

 natiuscula ; anfractibus quatuor, rotundatis, obsoletissime 

 transversim striatis, marginibus superne decurrentibus, 

 sutura subcrenulata ; apertura circulari, superne acuminata, 

 peritemate tenui, minime reflexo ; umbilico parvo ; operculo 

 spirali anfractibus paucis, leviter oblique striatis. 



Shell nearly round, whitish, with brown bands, smooth ; 

 spire slightly acuminated ; volutions 4, rounded, very obso- 

 letely transversely striated, with the upper margin decurrent ; 

 the suture irregularly crenulated : aperture circular, acumi- 

 nated at the upper part ; peritreme thin, not at all reflected ; 

 umbilicus small ; operculum spiral, its volutions few, slightly 

 obliquely striated. 



There are several varieties of this species, one of which has 

 the whole of the volutions slightly grooved. This last 

 is not the C. sulcatum of Draparnaud , nor is it very nearly 

 related to the common C. elegans. Teneriffe. 



50. C. elongatum. (pi. xxiv. f. 64.) 



T. oblongo-subpyramidali, decollata, pallide ferruginea : 

 anfractibus 4. spiraliter striatis, interstitiis decussatis ; sutura 



