36 STROPHOCHEILUS-BORUS. 



This is unquestionably a Borus of the B. crenulatustype, although 

 the form is slender and the suture smooth. The large nepionic shell 

 is distinctly demarked from the after-growth. 



S. LUTESCENS King. PI. 12, fig. 59 ; pi. 9, figs. 46, 47, 48. 



Shell perforate, ovate, rather thin (or in a variety, thick and 

 solid), covered with a thin pale yellow cuticle. Surface with incon- 

 spicuous growth-wrinkles and minutely decussate granulate. 

 Whorls 4*, the first one planorboid, the last ventricose-oval ; suture 

 linear, impressed, descending and then ascending at aperture. Aper- 

 ture ovate; outer lip narrowly expanded, thin or thickened, orange 

 or brownish ; columella expanded and vaulted over the perforation ; 

 parietal callus thin, transparent. 



Alt. 26i-27 ; diam. 19-20 mill. ; aperture, alt. 16-16 mill. 



S. Uruguay, at Montevideo (Paz, Martenez, et al.} ; Maldonado 

 (King). 



Bulinus lutescens KING, Zool. Journ. v, p. 340. Bulimus lutescens 

 PFR., Monogr. ii, p. 49 ; vii, 46. MARTENS, Novit. Conch, v, p. 23, 

 with var. australis. Bulinus nucleus SOWB., Conch. Illustr. f. 33. 

 REEVE, Conch. Icon. f. 99. DESH., in Fer. Hist. p. 37, pi. 139, f. 15, 

 16. ORB., Voy. dans 1'Amer. Merid. p. 305. STROBEL, Malac. 

 Argent, p. 20. 



Distinct from all the foregoing species (except S. bridgesi) in the 

 non-crenulated sutures and absence of riblets or other special sculpt- 

 ure on the earlier whorls. 



Var. australis Martens. PI. 9, figs. 47,48. 



Similar to lutescens, but when adult rather heavier, the peristome 

 much thickened as in S. pachychilus. 



Alt. 29J, diam. 20 mill. 



Bahia Blanca, Prov. Buenos Ayres, Argentina (Orbigny ; U. S. F. 

 C. Str. ' Albatross ') 



The lip is somewhat thickened also in some of the specimens before 

 me from Montevideo, though less so than in those from Bahia 

 Blanca, which lies nearly 10 degrees further south. On the other 

 hand, some of the specimens apparently quite adult, which I 

 have seen from Bahia Blanca, have the lip thin ; so that the variety 

 is of but slight value. 



