23S LECTURES ON MOLLUSCA. 



Family Dotonid;e. 



In this family, the tongue-ribbon is narrow, with a single series of 

 recurved, serrated teeth. The gills are in two rows of shrub-like pro- 

 cesses along the back, into which the liver-vessels enter. In Hero, 

 Gellina, and Nerea the tentacles are not retractile ; but in Doto and 

 Melibe, they are slender, and can be drawn into the graceful sheaths 

 which support them like a candlestick. 



The Chiorcera of Puget Sound may perhaps belong to this group. 



Family Glaucid/E. 



Glaucus is a very singular creature. The foot is rudimentary, and 

 it swims in the open sea, feeding on Jelly Fish and Veldlas. The gills 

 are arranged on side-fins, spreading out like the snake-tails on a 

 gorgon's head. The teeth have some resemblance to those of Amoria 

 among the Volutes, but are serrated on each side of the point. 



Family iEoLiDiE. 



The AEoli's tribe are very delicate, graceful, highly ornamented, and 

 beautifully painted mollusks, which live in shallow water, principally 

 preying on zoophytes. In confinement, they have been known to 

 browse on the breathing ornaments of their fellows, or even to devour 

 each other's bodies. The gills are arranged as very numerous stamens, 

 in variously-grouped rows along the hack. Into these enter the rami- 

 fications of the stomach and liver. The tentacles are generally simple 

 and unadorned. The teeth consist of a single series of semicircular 

 combs. The other generic forms are Calma, Flabellina, Facellina, 

 Coryphella, Favor inus , Phidiana, Cuthona, Cavolina, Galvina, Tergipes, 

 Embletonia, and Calliopwa. In the last genus the back-tentacles are 

 obsolete. They are all characterized by having the last vessel of 

 the liver stomach above the ovary, instead of below as in the previous 

 families : but agree with the others in having only one orifice to the 

 reproductive organs. 



Family Fionhle. 



In this and the next family there are two openings for the repro- 

 ductive organs, and two hind vessels for the liver-stomach. Fiona 

 has four tentacles, jaws round the mouth, and a fringe on the inner 

 side of each gill-stamen. 



Family Herm^eidje. 



Hermcea and Stiligcr have only two tentacles and no jaws. The 

 little Alderia, from the salt marshes of Skibbereen, has no tentacles 

 at all. 



Family Elysiadje. 



In all the previous families, the gills have appeared the most beau- 

 tiful and important organs of the Nudibranchs. In the rest, 'they are 

 no longer seen. Elysia and Placobranchus breathe by means of cilia 



