92 



mantle when about to suspend its function of calcification, expands itself 

 into several dictations, of considerable length in some species, each secre- 

 ting a massive claw, winch it ultimately fills with calcareous matter, the 

 hinder one being thrown over the spire so as almost to conceal the primitive 

 growth of the shell from the observer ; the mantle then withdraws, and 

 subsiding in wrinkles, deposits that richly coloured layer of corresponding- 

 wrinkled enamel with which the columella and aperture are always adorned 

 at maturity. 



The Pterocera, or ' Spider Shells ', are few in number, but well charac- 

 terized by their distinctions of colour, and the number and growth of their 

 claws ; they are all inhabitants of the tropical seas. 



1. aurantia, Lam. 



2. chiragra, id. 



3. elongata,* Swain. 



4. lambis, Lam. 



Species. 



5. millepeda, Lam. 



6. multipes, DesJi. 



7. pseudo-scorpio, Lam. 



8. rugosa, Sotc. 



9. scorpio, Lam. 

 10. truncata, id. 



Figure. 



Pteroceea multipes. PI. 8. Fig. 40. Shell, showing the digitated ex- 

 pansion of the lip, and wrinkled surface of the aperture. 



Genus 6. STROMBUS, Linn&us. 



Animal ; similar to that of Rostellaria, and Pterocera. 



Shell ; oblong-ovate, emarginated and recurved at the base ; spire 

 conical, somewhat turreted ; lip expanded, not digitated, and 

 sinuated toioards the base ; aperture oblong, rather narroiv, 

 slightly emarginated at the upper part. 



Eegarding the soft parts, the Stromli are identical with the Rostellaria 

 and Pterocera already described, and the peculiarities of which it is un- 

 necessary here to repeat ; but the shell presents an uniformity of character 

 sufficiently distinct from either to merit attention. The base is not pro- 



* I cannot .agree with M. Deshayes in the propriety of naming this shell "Pterocera novem. 

 dacfylis "; the noim-abhitive is ungrammatical in the sense required by the binomial form of 

 nomenclature. Chemnitz was undoubtedly the tirst describer of the species, and a very charac- 

 teristic figure is it accompanied with ; but, as was almost invariably the case with his precursor 

 Martini, he omitted to distinguish it by any specific name. The words above quoted, form part 

 of Chemnitz's description, — " Sfrombvs novem daetylis instructus", &c. , and Swainson is 

 therefore justly entitled to the priority of having named the species. 



