206 RETUSA. 



Var. PELLUCiDA Brown, PI. 23, %. 68. 



Smaller, shorter, thinner and more transparent, slightly less 

 strongly ribbed or sometimes quite smooth ; epidermis slightly 

 prismatic (Jeffr.). 



Scotland and Norway, 



R. TRUNCATELLA Locard. Unfigured. 



Subconic-elongated, well contracted and longitudinally plicate 

 above, with two opaque bands at middle and base of the last whorl. 

 Spire quite concave ; last whorl highest at its upper extremity, with 

 straight profile; columella feebly folded. Alt. 3-4, diam. I5-2 

 mill. (Loc). 



Mediterranean 



Cyliclma truncaiella Locard, Prodr., p. 73, 533 ; Coq. Mar. des 

 Cotes de Fr., p. 28, 1892. 



R. SEMisuLCATA Philippi. PI. 23, figs. 70, 71, 72. 



Shell thin, cylindrical, elongated, truncated at summit, visibly- 

 constricted around the middle, and dilated at base. Spire a little 

 concave, composed of 3 or 4 visible whorls separated by a well- 

 marked suture. Surface of the las^t whorl traversed from summit to 

 middle by numerous nearly vertical longitudinal folds. Aperture 

 elongated, narrow above, dilated and pyriform toward the base; lip 

 simple, sinuous, a little bent in the middle; columellar margin very 

 feebly sinuous. Columella thick, arcuate and twisted at base. 

 Color milk white, nearly opaque, with a wide, descending, more 

 transparent band below the middle, and sometimes several narrow 

 transparent lines below it. Alt. 3*2, diam. r33 mill. (J5., D. D.) 

 Mediterranean and Adriatic Seas, littoral and laminarian zones. 



Bulla semisulcata Phil., Enum. Moll. Sicil. i, p. 123, pi. 7, f. 19. 

 — Retusa semisulcuta BuQ., Dautz. & Dollf., Moll. Rouss., p. 530, 

 pi. 64, f. 15-17.—?? Bullina striata Risso, Hist. Nat. Eur. Merid., 

 iv, p. 52. 



More elongated than R. truncatula, with straighter longitudinal 

 folds, and a wide transparent zone. 



R. MAMiLLATA Philippi. PI. 23, figs. 65, 66, 67. 



Shell convoluted, subpellucid, shining, truncated at summit, of 

 a regularly cylindrical form, a little constricted in the middle. 

 Spire composed of 3 whorls, the first globular and projecting ; suture 

 profound. Sculpture consisting of exceedingly finely punctured 

 spiral striae. Aperture narrow, nearly linear above, dilated and 



