CYCLOSTREMA. 287 



Shell orbicular, white or of a uniform colour : spire more 

 or less depressed, of few whorls : mouth nearly circular, with 

 a free and continuous peristome : umbilicus distinct and deep. 



All the British species are minute. They appear to 

 be ovoviviparous, producing their spawn inside, and de- 

 positing it on extraneous substances to be developed ; the 

 spawn contains fry perfectly formed and having com- 

 plete shells. The genus was founded by the celebrated 

 novelist, Captain Marry at, by whom its characters 

 were thus briefly described in the 12th volume of the 

 'Transactions of the Linnean Society' (1818) : "Testa 

 depressa, perspectivo umbilicata; apertura circularis." 

 He referred the Helix depressa and H. serpuloides of 

 Montagu to this genus : but the animal of the former 

 resembles that of a Rissoa, and is the type of Fleming's 

 genus Skenea; the other is correctly assigned to the 

 present genus. Delphinula of De Roissy or Lamarck 

 has rough and angular whorls — although perhaps 

 Philippi was right in adopting it for some of the species 

 now under consideration. Fleming's genus Cyclostrema 

 is very different, being represented by Rissoa Zetlandica. 

 It is unnecessary to say of the genus Delphionoidea or 

 Delphinoidea of Brown, which has been suggested by 

 the Messrs. Adams, more than that it is both superfluous 

 and heterogeneous. 



1. Cyclostrema Cutleria'num * Clark. 



Skenea CutJeriana, Clark, in Ann. & Mag. Nat. Hist, new ser. vol. iv. 

 p. 424. 8. ? Cutleriana, F. & H. iii. p. 164, pi. lxxviii. f. 3, 4. 



Bout clear-white : pallial lobes or neck-lappets distinct : 

 head rather long, broad, and finely wrinkled across : tentacles 

 rlattish, liueated down the middle, exquisitely but rather 



* Named in honour of Miss Cutler, a lady of scientific taste and 

 acquirements. 



