146 



of the genera of this extensive series of vegetable feeders, the foot is limited 

 in size and its operculum is horny. 



It is somewhat curious that in a genus numbering nearly a hundred 

 species, of which most are inhabitants of equatorial seas, there is so Kttle 

 indication of colour. Where such exists it is extremely effective, the ground 

 colouring of the whorl being of a rich semitransparent brown, whilst the 

 rings are white, as in the S. Pallasii; and it is equally worthy of remark 

 that the most highly coloured species, the 8. communis of our own shores, is 

 that which inhabits the coldest region. 



The species are chiefly characterized by the difference in the number and 

 developement of the rings, which it may be remarked are formed at 

 intervals by the reflected margin of the aperture, and are always alike in 

 individuals of the same. Unlike other shells of this family in which the 

 lip is rarely reflected until the animal arrives at maturity, the formation of 

 rings commences after tliis manner from a very early period of growth, and 

 these, less complicated in structure, are analogous to the varices of the 

 canaliferous tribes. In the well-known Scalaria pretiosa of the China Seas, 

 the rings or varices are situated at moderate intervals, increasing in area in 

 exact geometrical proportion with the size of the shell ; in S. imperialis 

 they are of the same comparative substance, but developed at much more 

 frequent intervals ; in S. lyra they are extremely fine, having almost the 

 appearance of silken threads ; in S. raricostata they are only deposited at 

 remote intervals, and with considerable irregularity ; and in 8. alata they 

 are characterized at the upper part by the addition of a curious wing-like 

 process, of wliich there are various indications more or less strongly exhi- 

 bited in many species. The most aberrant form of the genus is the 

 8. magnifica, in which the whorls are contiguous, and the typical pecu- 

 liarity of the genus seems scarcely to enter into its plan of growth, there 

 being only a few shght rings at irregular intervals on the last two whorls. 

 In composition and texture this shell is, nevertheless, a 8calaria, and 

 affords an important Hnk with Turritella. 



Among the localities noted by Mr. Sowerby in his beautiful monograph 

 of this genus lately published in the ' Thesaurus Conchyliorum,' are the 

 following : — Eastern Seas principally, West Indies, Pacific Islands, Califor- 

 nia, and New Holland. 



Species. 



1. aciculina, Hinds. 5. albilineata, Soic. 9. bicarinata, Sow. 



2. aculeata, /Sbw;. 6. angulata, /S'a^'. 10. bulbulus, i(/. 



3. acuminata, id. 7. am-ita, Sow. 11. buUata, id. 



4. alata, t¥. 8. australis, Lam. 12. Catanauanensis, ^<?. 



