XX 



THAUMASTUS. 



rupted wrinkles, or thimble-pitted by regularly anastomosing wrinkles. 

 Aperture less than half the shell's length, ovate, the outer Up obtuse, 

 not expanded or but slightly so. Columellar lip reflexed, usually 

 adnate, the short columella with a weak fold or none. 



Anatomy known from a specimen of T. magnificus from Piquete, 

 Sao Paulo, Brazil, sent by Dr. H. von Ihering. The long lung is 

 densely veined anteriorly, and posteriorly between the kidney and 

 intestine (pi. 49, fig. 9, nat. size. The preparation figured has been 

 extensively torn, as indicated). The kidney is triangular and as 

 long as the pericardium. The secondary ureter is a closed tube 

 throughout. 



The genital system (pi. 51, fig. 19, nat size), is Bulimuline. The 

 penis is enlarged in the middle (fig. 17), having very thick, mus- 

 cular walls and a small lumen (c). It is contracted above, plicate 

 within, and receives the vas deferens some distance below the apex 

 (see fig. 17). The retractor muscle is terminal. The base is en- 

 circled by a sheath, within which a loop of the vas deferens descends 

 (fig. 18). The vagina is short, plicate within. The duct of the 

 spermatheca is very long, and becomes abruptly narrower in the 

 middle (pi. 51, fig. 21); its lumen has finely plicate walls. 



The jaw (pi. 57, fig. 60) is composed of about a dozen broad flat 

 plaits, well consolidated. 



The radula has 44, 1, 44 teeth (pi. 57, fig. 61). The centrals are 

 tricuspid, laterals and marginal teeth bicuspid, of the ordinary 

 Helicid type commonly occurring in Bulimulus. The splitting of the 

 ectocone of tooth 18, figured, is somewhat abnormal. 



In T.foveolatus Binney found the jaw with over 50 delicate ribs, 

 teeth 34, 1, 34, without side cusps on centrals and laterals. 



Distribution, southern Brazil and Bolivia to the head waters of the 

 Amazon in Peru and Ecuador. 



I formerly considered this group a subgenus of Strophocheilus, on 

 account of its comparatively large nepionic shell ; but the anatomy 

 of T. taunaisii var. magnificus shows Thaumastus to belong near 

 Bulimulus, Auris and Plekocheilus. It has nothing to do with 

 Strophocheilus. The sculpture of the apex repeats patterns occurring 

 in Bulimulus. The teeth, jaw and genitalia are Bulimuline in their i 

 main features. The reticulation of the lung is like that of Anns 

 egregia. 



The species fall into four groups, as follows : 



