216 MAG1LUS. 



life the shell of a Magilus shall become tubular ; and as for the 

 operculum, it is certain that some, if not all, the species 

 enumerated as Leptoconchus by authors have been found with 

 opercula ; notably, we have figured the genuine operculum of 

 L. Lamarckii, Desh. The Isle of Bourbon, the Mauritius and 

 Sandwich Islands perhaps most islands with reefs atibrd. 

 homes to the Magili. 



We agree with Mr. Sowerby ; indeed, it would be impossible 

 to designate from the shells which species should be referred to 

 Leptoconchus and which ones to the juvenile condition of Magilus. 

 It is probable that the development of the tube is accidental, and 

 it is equally probable that, as in Conus, the operculum is not 

 always developed. Troschel has not discovered any indication 

 of armature upon the lingual ribbon. So irregular are the shells 

 of the Magili and so much is their growth influenced by the 

 circumstances of their habitation that all the species that have 

 been differentiated from M. antiquus must be regarded with sus- 

 picion. When immense numbers of specimens, from different 

 localities, and collected with a view T to coallescence rather than 

 to differentiation shall have been compared, we shall be able to 

 assign definite places to the species which we are now compelled 

 to take on probation. 



M. ANTIQUUS, Lam. PI. 68, figs. 400-411. 



Red Sea, Isle of Bourbon. 



M. Djedah (fig. 403) and M. tennis (fig. 404), Chenu, are 

 certainly synonymous. M. microceplwlus, Sowb. (fig. 401), is 

 separated with some doubt by its author on account of the small 

 size of the spiral nucleus and rapid enlargement of the tube ; but 

 I think that the position taken by the mollusk, in this case was 

 so restricted as to prevent spiral growth to the usual dimensions, 

 and the sudden increase in the size of the tube is evidence that 

 such was the case. 



M. Cuvieri, Deshayes (fig. 405), is a well-formed young speci- 

 men from the Isle of Bourbon. M. ellipticus, Sowb. (fig. 408), 

 M. striatus, Riippell (fig. 406), M. Peronii, Lam., M. serratus, 

 Desh. (fig. 401), M. rostratus,A. Ad. (figs. 409, 410), M. Schrenkii, 

 Lischke (fig. 411), are all too close in form, and had better be 

 considered synonyms. The latter is from Japan. 



