30 STROPHOCHEILUS-BORUS. 



Bidimus roseus MONTFORT, Conch. Syst. p. 259, pi. 65. Helix semi- 

 lineata MKE., Synops. (1), p. 75. Ampullaria rosea SPIX, Test. Bras, 

 p. 3, pi. 4, f. 3. 



This is by far the most widely distributed of the Borus group, and 

 is correspondingly abundant in collections. The largest specimen I 

 have seen measures 132 mill, long (collection of Chas. W. John- 

 son). The smallest, from Mocambo, Brazil, collected by J. G. 

 Anthony, measures 74 mill. long. 



The spire is always conical, erect and elongated, the apex acute 

 for a Borus. The distribution of this species noxth of Tobago I 

 regard as probably effected by man. 



Var. CRASSUS Albers. PL 15, fig. 20. 



Shell very thick and heavy throughout ; aperture smaller, shorter, 

 the roseate lip much thickened by additions on its face ; parietal 

 callus rosy, thick, with a lump above. 



Alt. 86, diam. 53, aperture alt. 43 mill. 



Parana region (Orbigny, Giilich). 



B. oblongus var. crassa ALB., Die Hel. 1850, pp. 142, 144. MAR- 

 TENS, Novit. Conch, v, p. 19. B. hcemastoma Sows., Conch. Illustr. 

 f. 103, left side. FERUSSAC, Hist. pi. 146, f. 3, 4.B. oblongus var. 

 ORB., Voy. dans 1'Amer. Merid. p. 298, pi. 37, f. 1 (living animal) 

 etc. 



The specimen figured on pi. 15 weighs 3? oz. 

 Var. TOBAGOENSIS Pilsbry (n. v.). PL 14, fig. 70. 



Like oblongus in size and general form, but pure white through- 

 out under a deciduous yellow cuticle (rarely, if ever, entirely re- 

 tained in the adult) ; the mouth porcelain-white or ivory-white ; lip 

 reflexed, thin or thickened ; colurnella more distinctly folded than 

 in the type. Alt. 89, diam. 52 mill. 



Island of Tobago. 



A considerable series of Tobago specimens is before me, collected 

 by Dr. Benjamin Sharp and Thomas Bland, all albinos with well- 

 developed columellar fold. All records of oblongus from that island 

 refer to the white variety ; and I, therefore, believe it to represent 

 a constant insular subspecies. No specimens from other localities 

 among the 50 or more which I have examined, are albinos. Von 

 Martens states that he knew of no white-mouthed examples ; so 

 that it is moderately well established that such do not occur in con- 

 tinental South America, or if they do, are exceedingly rare. 



