238 



ZOOLOGY. 



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

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



"Fi?. 176.— Development of D^nlalvnn. A, monila ; B, trochosphere ; C, annn- 

 lated larra ; ZJ, lan'a with Its rudimenlary shell ; z, velam ; «. sh< 11 ; E. yooDg mnch 

 farther advanced, the shell or body segmented ; rf, rudimentary teutaclt^- ; j, snb- 

 <Esophageal nerve-ganglia ; //', digestive canal, and liver (/') ; the foot protrudes 

 from the shell. AlTmagnifled.— After Lacaze-DntMers. 



Bentalium are distinct. The young is a trochosphere and 

 afterwards becomes segmented, and the nnivalTe 

 shell then appears. (Fi^. 176.) 



Order 2. Pteropoda. — 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), ne 

 on each side of the head. The shell is conical 

 or helix-like. The species are hermaphroditic. 

 Cavolina tridentata Lamarck and Siyliola vitrea 

 VerriU (Fig. 178) are pelagic forms, occurring on 

 wg 177. -Den- the high seas, and are occasionallv taken with the 



rum. Used as tow-net ofE the southern coast of Xew England. 



shell money. — . ■ -r-\ i ■ r y • 7 



Afiersteams. Ltmacina arctica Fabr. is of the size of, and 

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

 It is common from Labrador to the polar regions. 



