o/Physa acuta (Drap.) in England. 115 



upon them ; behind, it sends forth four (sometimes three) minute 

 digitations, of which three, ahnost rudimentary, he on the body; 

 the fourth, somewhat larger, occupies the angle formed by the 

 junction of the outer lip and body; in front, five or six short 

 digitations are spread fan-fashion upon the reflected lip of the 

 columella; one, two, or even three of these (those nearest the 

 head) are often quite rudimentary. The armature of the lingual 

 membrane does not differ materially from that of P. fontinalis, 

 the denticles being similarly serrulate. 



Shell long ovate, acute, thin, transparent, horn- coloured, and 

 glossy; length 5^ lines, breadth 2^ to 3 lines. Whorls four 

 and a half to five and a half, swollen, with longitudinal, curved, 

 microscopic striola3 ; suture deep. Mouth occupying about half 

 the total length, apple-pip-formed, contracted above, slightly 

 expanded and produced below ; outer lip simple, acute ; pillar- 

 lip twisted, the swelling body-whorl projecting into and con- 

 tracting the mouth above, while, below, the lip is strongly 

 reflected upon the columella, and by its reflexion forms a distinct 

 narrow umbilical chink. 



The Physa from which the above description is taken has 

 recently been met with in one of the water-tanks in the Botanic 

 Gardens at Kew, Mi*. Choules, the discoverer, to whom I am 

 indebted for specimens, succeeded in tracing the species thence 

 to its original habitat — a ditch in the immediate vicinity of 

 London, whence it must have been introduced into the Gardens, 

 attached to aquatic plants. I abstain from mentioning this 

 locality, as Mr. Choules fears lest the rapacity of collectors 

 should exterminate this interesting addition to our list of inland 

 Mollusca. 



The ordinary form of Physa acuta as found on the Continent 

 differs considerably from our shell in being much larger, more 

 solid, opake, greyish-white, and having the throat generally 

 pinkish ; the body-whorl is also less swollen, and the pillar-lip 

 consequently less twisted. I have received, however, a form 

 similar to our own from Mr. M'Andrew, who took it at Seville ; 

 and the same variety is among the West Indian shells of M. 

 d'Orbigny's collection in the British Museum. It would seem 

 to be Moquin-Tandon's variety 7. minor, which he thus distin- 

 guishes from the type — " Coquille plus petite, plus ventrue, 

 mince, assez transparente.^^ Many of our specimens are girt 

 with fine, opake-white, spiral lines, thus evincing a tendency to 

 opacity. 



The Bulla rivalis of Maton and Rackett has of late years been 

 regarded as an erroneously introduced West Indian shell. The 

 description in the ' Linuican Transactions,' however, sufficiently 

 accords with P. acuta (to which shell, indeed, Moquin-Tandon 



