SIGARETUS. 



can most easily be distinguished by their want of the 

 dorsal perforations. With the Lamarckian genera Sto- 

 matia and tStomatella, they might much more easily be 

 confounded^ but the substance of their shell is never 

 pearly ; they are partly internal shells^ and the aperture 

 is always more or less modified by the last turn of the 

 spire. 



The fossil species are few and rare ; they occur in 

 the London Clay at Barton^ and in the contemporaneous 

 formations in France and Italy : the species in the Cal- 

 caire grossiere at Grignon, has a small umbilicus. 



We know not why Lamarck has arranged Nerita 

 cancellata of Chemnitz^ with Sigaretus rather than with 

 Natica. Much confusion seems to reign in Lamarck's 

 synonymy of his Sig. haliotoideus^ inasmuch as he quotes 

 figures of several very distinct shells for it; witness his 

 reference to Martini Conch. L t. 16. f. 151 to 154, and to 

 Bulla velutinaj Midler Zoolog. Dan. IIL t. lOL f . 1 to 4, 

 which is an external shell, and in our opinion, identical 

 with the English Helix laevigata. 



Upon examination of the specimens in the British 

 Museum, we are convinced that De Blainville's Cryptos- 

 toma Leachii, is the same as one of the two shells which 

 Adanson calls Sigaret ; his Crypt, hreviculum is probably 

 the other ; but this we cannot ascertain, because the shell 

 has been taken away from the specimen in the British 

 Museum. We have no doubt, however, that the Crypt, 

 hreviculum of De Blainville, is a female specimen of 

 Cuvier's Sigaretus, given by him to Dr. Leach. It is to be 

 regretted, that Cuvier has not given any description of 

 the shell of his Sigaretus, so that it is impossible to 

 ascertain whether or not it be identical with either of 

 Adanson's shells; it is, perhaps, needless to add, that 

 unless it can be identified with one of them, it ought not 

 to be considered as a Sigaretus. Its animal is certainly 

 very diiferent from that of Cryptostoma Leachii, which we 

 believe to be identical with one of Adanson's. 



Fig. 1. Sigaretus concavus, Lam. 



2. haliotoideus ? 



3. Leachii. Cryptostoma Leachii, De Bl. 



4. ^ ' • ■■ ■ canaliculatus, Defr. 



