the Caribcean Islands. 539 



trum latus prope anum (maris) positus ; apice attenuate, basi 

 appendiculato, glandulifero ; appendice perforate. 



Testa dextera, vestita, tenera, longitudinaliter plicata, globosa, 

 valde ventricosa. Spira depressa, vel brevis : anfractu ultimo 

 prgegrandi : basi late umbilicato. Peritrema simplex,* semper 

 tenue, raro subreflexum. Apertura integra, oblonga, maxima, 

 expansa. 



Motus segnis ; respiranda superficiem petit et alam sinistram 

 cervicis in tubum rigidum convolvit. Dum inspirat tentacula 

 flectit caputque motu lento retrahit, aerera apice siphonis acci- 

 piens. Vitae tenax. 



* Testa valde globosa ; umbilico majori. 

 Ampullaria duhia. 



Amp. flavescens, fuHginoso marmorata; siphone respiratorio 

 flavo, atro irregulariter fasciato : solea livida. 



Testa olivaceo-viridis, fasciata, fasciis obscuro-purpureis, latis : 

 spirS, rufescente, brevi : apertura pallide crocea, nebula livido- 

 purpureib sufFusa : operculo superne fusco, in feme castaneo- 

 nitente. 



Habitat in fluviis Americae aequinoctialis valde frequens, 

 spira saepe corrosa. 



Species affines Amp. luteostoma, et Amp. fasciata. Swains. 



Var. a. fasciis obliteratis.+ 



Var. /3. testa castaneo-viridi. 



Tab. Supp. xxvii. Fig. 7. Amp. dubia^ (var.) serpens. 

 «, Operculum, 6, Sipbo dexter, c Sinister. — 8. Eadem respiranda 

 ad superficiem aquae adscendens, siphone respiratorio exserto. 



* The species with subt^staceous opercula and a margined Peristome, form 

 my genus Pachystoma, the type of which is Ampullaria globosa of Swainson. 

 Zool. Illus. 



+ This variety I received alive with the Ceratodes from a small river in the 

 Gulph of Paria, and its inhabitant is here figured : it is a coarser shell than one 

 which my brother sent me from the canals of Demerara : in these quiet waters 

 the bands are distinctly painted. I have no doubt, from the examination of 

 many specimens, that they are mere varieties. 



