LECTURES ON MOLLUSCA. 195 



enamel, till the proper pattern has been given. A line is generally 

 seen on the back of the shell, where the two flaps met. The Cowries 

 are very pretty animals, with the mantle-lobes generally adorned with 

 fringes or ornamental painting. The breathing pipe is very short, and 

 often fringed also. They have long, slender tentacles, with eyes mid- 

 way up. The foot is very large, but can be withdrawn, with the 

 mantle lobes, into the shell. The Cowries are shy, and crawl slowly. 

 They hide themselves in coral reefs and under crevices of rocks. They 

 are found in all tropical regions, but there are very few on the Ameri- 

 can coasts. The difference in this respect between the Pacific shores 

 of America and the Pacific Islands, is very remarkable. On the east 

 coast of South America no species has yet been found. 



The Cowries form no inconsiderable an item in trade; the larger 

 species being brought to port in great numbers, for sale as ornaments; 

 while one of the smaller species, Cyprcea moneta, is collected (as gold) 

 for money. It passes current in Africa, as the medium of exchange. 

 Many tons are annually brought over from the East Indies and the 

 Pacific Islands, to transport again to the negroes of the Senegambian 

 region. In 1848, sixty tons Were brought into Liverpool alone. 

 Cowries were found by Dr. Layard in the ruins of Nimroud. The 

 typical species have a singular excavation near the notch under the 

 pillar lip. 



In the pear-shaped Cowries, Luponia, this part is irregularly plaited. 

 In Aricia, the base is flattened by thick masses of shell, which project 

 over the sides. 



In the Trivia group, the foot is short in front, but greatly length- 

 ened behind : the breathing canal is long also. The shell is ribbed or 

 covered with pustules ; the ribs are carried round the lips, instead of 

 separate teeth ; and the pillar is scarcely excavated. All the very 

 small Cowries belong to this group. Cyprceovula is intermediate in 

 form between this and the next family ; while Erato has a shell 

 shaped like Marginella, with minutely crenulated lips and polished 

 back. The Cowries first appear in the later cretaceous beds, and are 

 now at the maximum of development. 



Family Ovulid^e. {Egg and Shuttle Shells.) 



As far as the shells are concerned, the Ovula may be described as 

 unpainted Cowries without teeth on the pillar lip. The animal also 

 is sufficiently like the Cowry, in general appearance. The teeth how- 

 ever in the only species examined {Ovulum ovum) are so unlike that or 

 any other known type, that their habits have probably some great 

 peculiarity to correspond. On each side of the short central tooth, is 

 a tall hooked lateral with jagged edges ; and on each side of that, a 

 very large fan-shaped tooth, bordered by a deeply-cut, curly fringe. 

 In Ovulum, the outer lip is turned in and toothed : in Calpurnus, the 

 shell is hunch-backed, with a curious wart at each end. In Carinea 

 there is a ridge across the back, and the lip is not toothed. 



But the most singular shell belonging to this group is the Weaver's 

 Shuttle, {Radius volva,) in which each end of the lip is produced into 

 a very slender canal, longer than the body of the shell itself. The 



