90 THE TEOCHI. 



PEARL-SHELLS. 



Of the shelled Mollusca which the dredge ever and 

 anon brings up, the Trochi are among the moat con- 

 spicuous for beauty. T. ziziphinus is exceedingly 

 oommon in deep water, and not rare within tide 

 marks. Its very regularly conic form, and the blotches 

 of dark purple that run in a spire round and round 

 the shell are pleasing to the eye ; and the ani- 

 mal, which crawls freely in confinement, is richly 

 coloured, being of the tint of a ripe melon, striped 

 with black. (See Plate 1.) One or two specimens 

 of a pure white variety of this species have occurred 

 to me. 



Though this is a shell of considerable size, it is ex- 

 ceeded in that respect, and (in the estimation of some 

 probably), in that of beauty also, by T. granulatus. 

 The latter is esteemed a somewhat rare shell, but in this 

 Bay, and off Portland, it is not at all uncommon. In 

 shape it is equally elegant with the former, the shell ta- 

 pering to a conical point, and displaying a surface 

 sculptured with spiral raised lines, each of which is 

 composed of a number of minute rounded knobs, like 

 a string of beads. Its texture is somewhat fragile, 

 and its colour a faint flesh-tint or yellowish white, 

 slightly dashed with purple. 



In captivity the animal is rather chary of displaying 

 itself; which is the more to be regretted since it is 



minute Tarris neglecta upwards, swarmed during the months of August, 

 September and October in 1852; and it is generally considered that the 

 latter part of summer and autumn is the most favourable season for 

 studying all the Medusae of our coasts. 



