BULIMULUS. xxxiii 



Section Ncesiotus Albers, 1850. 



Ncesiotus ALB., Die Heliceen, p. 162, -f- Rhaphiellus PFR. -f Pele- 

 costoma Reibisch (in part). Man. Conch., xi, p. 94. 



A group of rather small species, including all Bulimvlidee of the 

 Galapagos Islands. The surface is frequently wrinkled and gener- 

 ally striate spirally. 



The genital system (pi. 59, fig. 6, B. nux, after Binney) is simple. 

 penis long and slender, with terminal vas deferens. The duct of the 

 ovate spermatheca is about as long as the penis, much shorter than 

 the oviduct, and arises from the atrium. The jaw is composed 

 of numerous flat plaits, 12 in B. bauri to 18 in B. nux, and is similar 

 to that of typical Bulimulus. The radula has 15.9.1.9.15 teeth in 

 B. bauri, 13.9.1.9.13 in B. eschariferus var. ventrosus, 31.9.1.9.31 in 

 B. nux. The teeth (pi. 59, fig. 8, B. bauri, after Dall) are essen- 

 tially alike in many species examined, the centrals being tricuspid, 

 with the middle cusp large, as long as the basal plate ; laterals 

 bicuspid. The marginal teeth have a long, bifid inner cusp, and the 

 outer cusp is split into several denticles. In this last character only 

 does Nxsiotus differ from typical Bulimulus in what is known of the 

 soft anatomy, though the duct of the spermatheca is somewhat shorter 

 than usual in Bulimulus. The splitting of the outer cusp indicates 

 terrestrial rather than arboreal feeding. 



B. achatellinus Fbs., xi, 99. B. calvus Sowb., xi, 105. 



achatinellinus Pfr. B. nucula Pfr., xi, 106. 



achatinellus Ads. B. galapag&nus Pfr., xi, 107. 



B. nux Brod., xi, 100. B. eschariferus Sowb., xi, 108; 



nuciformis Petit. xiv, 152. 



v. incrassatus Pfr., xi, 102. rugulosus Rve. 



v. verrucosus Pfr., xi, 102. bizonalis Anc. 



v. asperatus Alb., xi, 102. subconoidalis Anc. 



invalidus Reib. v. pileatus Dall, xi, 109. 



B. approximatus Dall, xiv, 150. v. ventrosus Reib., xi, 109. 



B. rugulosus Sowb., xi, 103. B. perspectivus Pfr., xi, 110. 



v. infuscatus Anc., xi, 103. rugulosus Reib. 



v. nudus Reib., xi, 103. B. snodgrassi Dall, xiv, 150. 

 B. planospira Anc., xi, 104. 

 B. ustulatus Sowb., xi, 104. 



venustus Reib. 



