352 



LOWER IN VER TERRA TES. 



manipulation necessary in this work can only be acquired by expei'ience ; the general 

 shape must first be wrought out, care being taken to leave every projection rather in 

 excess, to be gradually reduced as the details and finish of the work are approached." 



About fifty species of helmet shells are known, all from the warmer seas. ( 'assis, 

 the largest genus, has its metropolis in the eastern seas, a few species being found in the 

 West Indies and in the Mediterranean. The species most used for cameos is the black 

 helmet, U. madagascarensis, in which the white outer layer covers a darker, almost 

 black, second layer. The external surface is not, as the common name would aj)par- 

 ently imply, wholly black. The whorls are a dirty white, and the outer part of the lips 

 are rosy, the black being at and near the edges of the aperture. It reaches a length 

 of nearly a foot. C. glauca, the species figured, is smaller ; it comes from the East 

 Indies. The other genera of the familv are Cas.ncJim'a, Oniscia, and Pachyhatron. 





^r- 



-'^^ 3;g^te ;^-c 



hum pcrihx, tun sliell. 



The members of the family Doliid^ are large, with thin shells, the whorls of which 

 are ventricose, the body whorl being very large, and ornamented with revolving ribs. 

 The animal is large, and is provided with a remarkably developed proboscis, which is 

 long, cylindrical and flexible. The foot is very large and lobed in front; the tentacles 

 arise from a distinct head, and the eyes are placed on small pedicels growing out from 

 the bases of the tentacles. In the young the shell is closed by an o])erculum, but it 

 disajijicars with growth. 



The sjiecies of Dolmm are moi-e or less globular, with a vei'y large ajierture, and 

 liave received the common name, tun shells, while the species of Ficula are known 

 from their shape as fig or pear shells. Both genera are tropical or sub-tro])ical, active 

 molluscs, living on animal food. The shells are not usually brightlj' colored, but the 

 animals themselves are handsomely marked. 



Last in the order comes the Teitonid^. In conchological characters it belongs 

 near the Muricidae, but in dentition, development etc., its place is here, the lingual 



