296 DESCRIPTION OF NEW 



I very much regret that the operculum did not accompany this specimen, suspecting, 

 as I do, that it will be found to differ from the genus Melania, and be somewhat like 

 31. transversa, which I propose above to bring into this group. The operculum of this lat- 

 ter species was described by me as having the polar point near the centre, and having 

 five revolutions.* 



Basistoma Edwardsii. PL XXX. Fig. 1. 



Testa striata, tiirrild, subcrassd, geniculate"/, tenebroso-comed; spird valde at t em/at a; suturis valde im- 

 pressis; anfraclibus planulatis; superne impressis, lincis crebrissimis instructis ; apcrlurd subgrandi, 

 ellipticd, in/us albidd, ad basim valde abscissa ; columella Isevi tortdque. 



Shell striate, turreted, rather thick, geniculate, dark hnrn-colour; spire very much drawn out; sutures very 

 much impressed; whorls flattened, impressed above, thickly covered with revolving lines; aperture rather large, 

 elliptical, white within, at the base abruptly cut ofF; columella smooth and twisted. 



Hab. River Tocatinus, South America, Amory Edwards, Esq. 

 My cabinet. 

 Diam. .50, Length 1.92, of an inch. 



Remarks. — This very beautiful and interesting shell is remarkable for the new form it 

 presents in the aperture. It is thickly striate all over the whorls, and looks like a suc- 

 cession of coils of rope piled on each other. The two lower whorls are impressed above 

 the middle, which gives it a geniculate character immediately below the suture. Between 

 the striae there are very minute sculptured points. The apex being eroded, the number 

 of whorls are not ascertainable, but they are probably about ten. The outer lip is very 

 sharply edged, and the central portion very much extended on a curve. The aperture is 

 about one-fourth the length of the shell. 



The form of this species reminds one of Achatina columna (Lymnea columnaris, 

 Lamarck,) which is however, a land shell. It is drawn out like it and has flattened 

 sides, with a cut at the base of nearly the same form. In other characters they are not 

 at all alike, the columna being sinistral, covered with granules, much larger and belong- 

 ing to a different genus altogether. 



I dedicate this fine species to my friend Mr. Edwards, to whom I am indebted for it 

 and many other interesting shells from the waters and banks of the Amazon. 



Melania perstriata. PI. XXX. Fig. 2. 



Testa striata, acuto-conoided, sublemii, cinnamomeo-bruned ; spird elevatd, suballemiatd, ad apice carinatd 

 ft granulatd} suturis impressis; anfraclibus seplenis, convexis ; aperturd parvd, ellipticd, ad basim angulald, 

 intus rufd; columella lievi. 



Shell striate, acutely conical, rather thin, cinnamon-brown; spire elevated, somewhat attenuate, at the apex 

 carinate and granulate; sutures impressed, whorls seven, convex; aperture small, elliptical, angular at the base, 

 reddish within; columella smooth. 



* Proceedings Zoological Soc, London, 1851, p. 187. 



