440 PROCEEDINGS OF THE ACADEMY OF [1896. 



James Island, under lava, Cuming in Lea Collection ; Chatham 

 Island, near the southwest end, at a height of about 1,600 feet, Dr. 

 Baur ; Chatham Island, Kellett ; Charles Island, Cuming and H. 

 M. S. Peterel. 



Jaw thin, horn colored, arcuate, of equal height throughout, with 

 blunt ends ; anterior surface with about 14 broad, crowded, flattish 

 ribs, reinforced along their outer edges ; the ends of the ribs broadi 

 squarely denticulating the upper and lower margin of the jaw. 



Radula long, thin, narrow ; formula 1 ; rhachidian tooth 



84-12-12+8 



stout, tricuspid, with very short lateral cusps ; perfect laterals, about 

 tvvelve in number, bicuspid, with very short outer cusps; marginals 

 low, wide, with a long bifid inner cusp outside of which the cutting 

 edge is broken up into four or five denticles of nearly equal length. 

 In its thin and ample shell, uniform reddish-brown color, and 

 narrow, well-defined peripheral pale band, this form resembles the 

 species of the mainland more than any other Galapagos species. The 

 transverse riblets on the nepionic shell are very fine and almost 

 always decorticated ; the granular spirals are almost microscopic, 

 and when fresh and perfect, bear small projections of the perio- 

 stracum. 



Bnlimulus (Nsesiotus) Simrothi Reibisch. Plate XVI, figs. 11, 12, 13 ; Plate XVII, 

 fig. 2. 



Biilimn/us { A'cFsioiits) Siinrothi Reibisch, Isis, 1892, p. 11, t. 2, fig. 2; 

 Stearns, Proc. U. S. Nat. Mus., XVI, pp. 414, 428, 18H3. 



Bulimuhis {Nccsiotits) tortuganus Dall, Nautilus, VII, p. 54, 1893. 



La Tortuga, grassy zone. South Albemarle, Baur; 1,000-2,000 feet, 

 in the moist region, Albemarle Island, Wolf. 



Herr Reibisch has kindly furnished a photograph of one of his 

 types of B. Simroihi with which I have compared my specimens of 

 tortuganus. Wolf's shell in the photograph appears smoother, with- 

 out the deeply indented markings, and exhibits color streaks in 

 harmony with the lines of growth which none of the specimens of 

 tortuganus do. Nevertheless, the two forms should probably be 

 united, especially as Reibisch's description agrees better than the 

 photograph as respects surface and color. As the specimens collected 

 by Wolf were more or less immature, the original diagnosis needs 

 some additional data. 



Jaw light horn colored, thin, membranaceous, arcuate, of equal 

 height throughout and with the ends blunt; anterior surface with 

 about 17 rather narrow, flat crowded ribs, with thickened outer 



