238 



ZOO LOOT. 



the preceding class, and is, by some authors, regarded as 

 the type of a separate class (Scaphopoda). The sexes of 



"Pi*. 176. Development of T>entalwnn. A, morula ; B, trochosphere; C, annn- 

 latcil larva ; I>, larva \\iili iis rudimentary shell ; z, velum ; </, *h< 11 ; E. young much 

 farther advanced, the shell or body segmented ; d, rudimentary tentacles ; j, sub- 

 <i-i>phas;eal nerve-ganglia; //".digestive canal, and liver (/'); the foot protrudes 

 from the shell. Alt magnified. After Lacaze-Duthiers. 



Dcntalium are distinct. The young is a trochosphere and 

 ;if upwards becomes segmented, and the univalve 

 shell then appears. (Fig. 176.) 



Order 2. Pteropodn. In these winged-snails 

 the head is slightly indicated and the eyes are 

 rudimentary ; while they are easily recognized by 

 the large wing-like appendages (epipodium), aie 

 on each side of the head. The shell is conical 

 or helix-like. The species are hermaphroditic. 

 (' roll mi f n't/i>>i f<tf a Lamarck and StyUola vitrea 

 'Yen-ill (Fig. 178) are pelagic forms, occurring on 

 Fie m.-Den- the high seas, and are occasionally taken with the 



tui i mn fin/ Kino- 7 J 



r>-d as tow-net off the southern coast of New England. 



chell money. . . -n i ,1 i 



After steams. Li //Kin HI/ arctica Fabr. is of the size of, and 

 'ooks like, a sweet pea moving up and down in the water. 

 It is common from Labrador to the polar regions. 



