AMPHIBULIMA. 233 



MONTFORT, Conch. Syst. ii, p. 90 (for A. cucullalus) Brachyspira 

 PFR., Mai. Bl. 1855, p. 117; Mon. Hel. Viv. iv, p. 804. MARTENS 

 in Alb., Die Hel., I860, p. 311 (type S. ligrina Les.) 



Shell Succinea-shapeQ) with less than 3 whorls, sculptured with 

 growth-wrinkles and more or less obvious spiral impressions or cords ; 

 columella distinct, not reduced to a spiral ridge, which exposes the 

 interior of the spire. Apical 1^ whorls finely wrinkled longitudi- 

 nally, the wrinkles waved, sometimes anastomosing to form a net- 

 work or quasi-punctulation, and usually slightly cut by spiral lines 

 on the latter part of the last nepionic whorl (this sculpture obsolete 

 in some forms). 



Soft parts externally about as in _Buh'?nithts, except for the degen- 

 eration of the mantle. Jaw thin, composed of many narrow plaits, 

 as in Drymceus. Radula with the mesocones prominent and broad, 

 blunt or pointed. Genitalia simple, as usual in Biilimulus and Dry- 

 mceus. 



Type, A. patula Brug. Distribution, Caribbean Islands. 



The shell is capable of containing the soft parts in the typical 

 forms, but not in the subgenus Pellicula. It closely resembles Su.c- 

 cinea in form, and the species were formerly referred to that genus. 

 The researches of Dr. Paul Fischer and Mr. W. G. Binney have 

 demonstrated the Bulimulid organization of all the main species of 

 the group, and malacologists now agree upon the systematic position 

 of AmphibuUma as a genus of Bulimulidce. 



Omalonyx (Homalonyx of some authors), a genus of Succineidtz, 

 has a shell closely resembling that of Pellicula, a subgenus of Am- 

 phibuUma. In genera with the shell degenerate, it is practically im- 

 possible to frame generic diagnoses which shall be really diagnostic. 

 Rliodonyx can scarcely be so defined conchologically as to distinguish 

 it from some forms ofSuccinea; PeUlcula is equally impossible to 

 distinguish from Omalonyx or some Polynesian Succineidce ; and 

 Gtzotis, Pel/e/ta, Cryptostrakon and some forms of Girasia have shells 

 so similar as to almost defy any attempt at differentiation, though the 

 soft parts show broad distinctions. 



AmphibuUma imbricata Rochebrune, Bull. Soc. Philomathique de 

 Paris (7), vi, 1881-2, p. 72, is apparently a Succinea. 



Key to subyenera and species. 



A. Shell with colored cuticle, streaked or spotted ; spire small but 

 projecting. AmphibuUma s. str. 



