TRUNCATELLA. 319 



is no peculiar advance nor market! basal retrocession of 

 its margin. The columella does not form any angle (as in 

 CJiemnitzia) with the upper portion of the inner lip, but 

 runs in the same obliquely subrectilinear line with it. The 

 axis is not perforated. 



The form in the young shell is tapering subcylindra- 

 ceous, and the apex is not truncated, but only very blunt. 

 The spire, previous to its decollation, consists of six volu- 

 tions, which are even more deeply and abruptly divided 

 than in the adult specimens ; the outer lip is acute and 

 simple. 



The majority of our English examples (what we have 

 from the Adriatic are larger and less deeply divided) 

 do not measure more than two lines and a third in length, 

 with a breadth of scarcely more than a third of that 

 measurement. 



The animal is of a yellowish white colour. 



An influx of fresh water seems essential to its existence. 

 It is obtained near Portland, and at Wyke, near Wey- 

 mouth, cast up dead at high water-mark (S. H.) ; at 

 Poole (Rackett) ; and also said to be picked up here and 

 there on the shore of South Devon, and at Southampton 

 in brackish water. Macgillivray states that it has been 

 taken in sea-sand from the Bay of Cruden, and Mr. Bean 

 enumerates it among the species taken at Scarborough 

 (could these examples have been transplanted in ballast ? 

 for it is mainly a southern shell).* 



* Pulteney, who first introduced the species into the British Fauna, appears to 

 have sent Montagu an exotic shell, which he regarded as identical with the 

 Dorset species. The author of the " Testacca Britannica " described the latter 

 in his work under the name of Helia: subcylindrica (p. 393, — Cyclostoma suhcy- 

 Undricum, Fleming, Brit. Anim. p. 258, probably), but expressed his doubts of 

 its indigenousness, stating it to be a common West Indian species (perhaps the 

 Tr. CarihtBensis of Pfeiffer's Monograph). It is, however, generally supposed 

 to be the Tr. (Cyclostoma) trimcatulu of Uraparnaud, a Mediterranean shell. 



