XX11 XENOTHAU.MA, BULIMULUS. 



Genus XENOTHAUMA Fulton, 1896. 

 This vol., p. 134. Type and sole species, X. baroni. 



This is pvobably, as I have elsewhere noted, a Scutalus specialized 

 in the whole structure of the post-nepionic shell ; but so divergent 

 that it deserves generic rank. 



X. baroni Fult., xiv, 134. Peru. 



Genus BULIMULUS Leach, 1815. 

 Man. Conch., x, p. 125. Type B. guadalupensis Brug. 



Shell varying from ovate-conic to oblong, column-shaped, or 

 rarely depressed and Helicoid; umbilicate or imperforate. Aperture 

 with the outer lip usually thin, sometimes expanded. Columella 

 straight or concave below, weakly folded above, the margin reflexed. 

 Apical whorls variously sculptured (but never with an even, minute 

 sculpture of pits in spiral and vertical series). 



The mantle generally bears two widely separated lobes. The 

 kidney is the length of the pericardium and triangular. The reticu- 

 lation of the lung is chiefly along the intestinal side, spreading to 

 the other .side near the pneumostome. The pulmonary vein domi- 

 nates, though sometimes the first branch of the vena cava is well 

 developed (pi. 53, figs. 30 to 33). 



The free retractors are typical of the family, the left tentacular 

 and pharyngeal bands being more or less united proximally, and the 

 right tentacular band arises from the face of the columellar muscle 

 (pi. 54, fig. 39, B. dealbatus). As in other genera of the family, the 

 columellar muscle is adnate throughout to the adjacent face of the 

 mantle. 



The genital system is simple. The penis is long and generally 

 twisted, the vas deferens and retractor muscle arising from its apex ; 

 it is generally encircled around the base by a muscular sheath. The 

 duct of the spermatheca is generally about as long as the oviduct. 

 Some branches of the right tentacular muscle band are attached to 

 the vagina and to the body-wall near the external opening. 



The jaw is arcuate and plaited, the plaits vertical in the middle, 

 not converging to form a triangular area (pi. 57, fig. 62, B, dealbatus 

 mooreanus). 



The radula has but slightly curved transverse rows of teeth, which 

 are of the normal Helicid form. In the rhachidian teeth, the large 

 mesocone usually is flanked by small etocones. The laterals have 



