84 PTEROPODA. 



truded from tlieir common slieatli, and form so 

 many adhesive suckers adapted to seize and hold 

 the minute objects with which they come into con- 

 tact. As there are six tentacles, and each tentacle 

 "bears 3,000 sheaths, and each sheath contains 20 

 suckers, it follows that there must be an array of 

 360,000 distinct organs capable of being brought 

 into play by a Clio in the act of seizing its prey. 



In the same animal there are a pair of jaws and 

 a tongue. Each of the former is a straight stem, 

 from one side of which project a series of arched 

 spines, so graduated in length that their points 

 reach the same level. The prey seized by these 

 many-toothed jaws is then taken hold of by the 

 tongue, which is a band covered with rows of 

 minute spines hooked backwards. 



Some of the species have the head and its organs 

 less distinct. 



Below the swimming-fins depends an oblong 

 body, which in some genera is enclosed in a deli- 

 cate shell of glassy transparency, varying in shape 

 in different species. Sometimes, as in Hyalea, it 

 resembles the two valves of a bivalve united at the 

 hinge, but narrowly open at the sides and front. 

 At other times, as in Cleodor^a, the sides are united, 

 and there is only a front opening. In Limacina 

 and Spirialis, again, it is a cone spirally twisted, 

 like that of a Snail, but in a reverse direction. In 

 those species which have a two-valved shell, the 

 valves are placed against the back and belly, as 

 in the Beachiopoda, and not on the right and 

 left sides, as in the Conchifera. 



AutIio7^ities, (&c. — To Cuvier's '^Memoires sur 

 mistoire et I'Anatomie des Mollusques;" to Van 

 Beneden's " Exercices Zootomiques " (Brussels, 



