206 RETUSA. 



Var. PELLUCIDA Brown, PI. 23, fig. 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. H-2 

 mill. (Loc.'). 



Mediterranean 



Cylichna truncatella 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 last 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. 1*33 mill. (J?., D. D.) 

 Mediterranean and Adriatic Seas, littoral and laminarian zones. 



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

 Retusa semisulcata 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 



