G54 ABRANCHIATA. 



SECOND ORDEE. DORSIBRANCHIATA, (Lat. dorsum, back ; Iran- 

 chia, gills.) 



These Annelidans have their organs, and especially their 

 branchiae, distributed nearly equally along the whole or a part 

 of the body. All the species are aquatic and worm-like, swim- 

 ming with facility and active in crawling. The head is distinct 

 from the trunk ; they are furnished with two pair of rudimen- 

 tary eyes. The order includes the Sea-Mice and the Sea-Centi- 

 pedes, arranged into several families or groups. 



FIRST FAMILY. Aphroditida, (Gr. from Aphrodite, Venus.) 

 SEA- MICE. 



These include species oval in form, some of which are su- 

 perbly colored. Usually they have two pairs of jaws. The 

 gills are concealed under two rows of scales covering the back, 

 and hidden by a kind of flocky down or tow, from which issue 

 brilliant spines or bristles. The species Aphrodite aculeata, 

 (Lat. prickly,) is six or eight inches long, and two or three 

 inches wide. Cuvier says that these Sea-mice do not yield in 

 beauty either to the plumage of the Humming-birds, or to the 

 most brilliant precious stones. 



SECOND FAMILY. Eunicida.' 



These are represented by the genus Eunice. This is fur- 

 nished with tuft-like gills, and has the trunk armed with three 

 pairs of horny jaws. Each of the feet has two cirri and a bun- 

 dle of bristles ; there are two tentacles on the head, above the 

 mouth, and two on the neck. The GIGANTIC EUNICE, E. gigan- 

 tea, found in the seas around the Antilles, is sometimes upwards 

 of four feet in length, being the largest annelidan known. 



THIRD ORDER. ABRANCHIATA, (Lat. a, priv. or without; Iran- 

 chi&, gills.) 



The Worms of this order are without branchiae, respiration 

 being accomplished by means of the skin. The order includes 

 two principal groups, of which the one is terrestrial, the other 

 aquatic. 



