HAUPxi. 103 



more fiilly developed than in the world of shells. The 

 inollusk of the Bolmm perdioc, for instance, is bright blue, 

 contrasted with a dull brown shell \ those of the D. olearmm 

 and pomum, of which the one is of a cerulean coloui', the 

 other of a rich coppery green, inhabit pale yellowish shells. 



The colours of such mollusks as pertain to the genus 

 Harpa are, on the contrary, scarcely less vivid than those 

 of the shells which they inhabit. They are often of 

 yellowish-green and rose tint, and curiously ocellated, 

 whilst the breathing-organ is transversely striped. 



The shells of this beautiful and very limited genus are 

 too well known to render any description necessary ; but 

 among them the Many-ridged Harp, the Eose Harp, and 

 David's Harp are, perhaps, the most distinguished. In 

 each, the prominent longitudinal ribs, which impart the 

 harp-like symmetry of structure to the shell, are regarded 

 as varices, analogous in structure to those of the Murex : 

 they form the margin of the aperture, and the intervals 

 between them are probably of rapid growth. 



Harim mostly inhabit the shores of Ceylon, the Mauritius, 

 and the PhiHppine Islands ; one species, the H. crenataj 

 is from Mexico. 



The genus Bolmm constitutes a limited, but very charac- 



