248 



ZOOLOGY 



The group of mollusks represented by Chiton (Fig. 202, 

 Chiton niber) have been referred to the worms by Jherhig. 

 on account of the segmented appearance 

 of the plated shell, and the nervous sys- 

 tem, which consists of two parallel 

 cords, connected by several commis- 

 sures ; * as well as from the fact that the 

 intestine ends at the hinder end of the 

 body. The young 

 is oval when hatch- 

 ed, and is a trocho- 

 sphere, having a 

 ciliated ring in the 

 Fig. 200. sing. Nat- middle of the body 



ural size. , i n /, a 



with a long tuit or 



large cilia on the head. Afterwards 

 it becomes segmented, as in Fig. 203, 

 and is remarkably worm -like, the 

 limestone plates of the adult corre- 

 sponding to the primitive larval rings. 

 Certain Gastropods are useful either 

 as food or in the arts. In Europe 



T -11 TII n v L i r> i -n Fig. 201. End of tentacle 



Lit ton na (iftorea, the limpet (Fatella of a snail t eye ; op optic 

 vulgata), the whelk (Buccinum un- llurve; > olfactory nerves ' 



datum), and the Koman snail (IL'li.r 

 ]><>ini(ti(() are eaten. The sea - ear 

 (Haliotis) is roasted in the shell. 

 The animal of Cymla, Strombits gi- 

 <jax. Turbo, Trorltiix, and Con tot are 

 eaten in the tropics, while many of 

 the larger forms are used for 1ish- 

 bait. Pearls are sometimes found in 

 the species of Holiuti* and Ttirbo. 

 The beautiful shell of Cassis is made 

 into cameo pins, and the shell of 

 giyas is in the West Indies made into ornaments. 



* In Fissurelln and Haliotis the two nerve-cords from the pedal gan- 

 glia are also iinited by nine transverse commissures, so that here also 

 we have an approach to the double ganglionated cord of worms. 



FIG. 20i. 



FIG. 203. 



Fig. 202.- Chiton ruber. 

 Fig. 203. Segmented larva 

 of Chiton. 



