BULIMULUS-DIVISION III. 83 



Fernando Noronha Island, off Brazil, living under bark of Mango 

 trees in the garden and on north side of island ; also at base of the 

 Peak, north side, under stones, and on Eat Island (Ridley). 



Bulimus (Bulimulus) ridleyi E. A. SMITH, Journ. Linn. Soc. 

 Zool., xx, p. 501, pi. 30, f. 9 (July 31, 1890). 



B. americanus Dall has a longer aperture and more broadly re- 

 flexed lip ; it is also somewhat larger. The spiral strise of B. ridleyi 

 are often scarcely discernable on specimens deprived of the cuticle 

 but otherwise well preserved. 



Mr. Smith writes : " I do not know any species sufficiently near 

 this form wherewith to offer a comparison. It resembles somewhat 

 in form certain species of Partula; it faintly recalls, chiefly on 

 account of color, B. jacobi of the Galapagos Islands, and the spiral 

 striation, although finer, somewhat resembles that of some of the 

 species of the genus Plecotrema" 



DIVISION III. Bulimuli with the nepionic whorls sculptured with 

 regular, straight or nearly straight vertical rib lets. 



The third division of Bulimulus is remarkable for the discontin- 

 uity of its distribution ; one group inhabiting eastern and north- 

 eastern South America, another the Galapagos Archipelago, and a 

 third, central and northern Mexico, Lower California and the south- 

 central and southwestern United States. This probably indicates a 

 former wide extension, with subsequent extinction in the region 

 geographically intermediate between the present habitats of the 

 groups. This contrasts with the distribution of the other two main 

 groups of the genus Bulimulus, both of which occupy continuous 

 areas. 



In many or most of the species of this division, adequate magni- 

 fication reveals delicate and close spiral strise between the vertical 

 riblets of the nepionic shell. This is an incipient condition of what 

 becomes conspicuous in Neopetrceus, a group which probably arose 

 from this stock. 



The shells of this division are almost invariably dull brown or 

 white, often more or less streaked obliquely, but very rarely banded. 

 The lip may be either simple or reflected ; and the contour, as in 

 Bostryx, varies within the widest limits. 



Three subgenera of this group are here recognized, separated 

 geographically and by the general appearance ; but it must be freely 



