POSCILOPODA. CRUSTACEA. LIMULUS. 339 



BRANCHIOPODA. 



The animals of this division are small, many of them micro- 

 scopic, and for the most part inhabiting stagnant fresh water. 

 Their feet are variable in number, solely adapted for swimming, 

 and some of them are constructed so as also to serve the purposes 

 of respiration. Their bodies are enveloped in a membranous 

 covering generally in the form of a shield. They are beautiful 

 objects for microscopic examination. Only a few have as yet 

 been observed. 



BRA'NCHIPUS STAGNA'LIS, LAM.; An. sans Vert.,v. 198. Cancer stag- 

 nalis, LIN.; MULL.; FABR. ; PENN. Gamarellus stagnalis, HERBST ; Cancr., ii. 

 121, pi. 35, f. 8 - 10. Branchiopoda stagnalis, LATR. j DESM. ; FLEM. 



This animal is often an inch in length, and is remarkable for its 

 numerous, fringed legs, which are kept in continual motion. 

 Found in stagnant pools. 



CYCLOPS. One species. 



PQECILOPODA. 



Characterized by having the feet of various forms ; those in 

 front being constructed for walking and prehension, and the hinder 

 ones for swimming and breathing. They are deprived of jaws, 

 and instead of them have organs for suction. Most of them live 

 on the bodies of other animals, principally fishes, whose juices 

 they suck for nourishment. The body is covered with a kind of 

 buckler, usually of only one piece. 



LfMULUS POLYPHE'MUS, LATR.; SAY; Journ. Acad. Nat. Sc., i. 433. 

 DESM. ; Consid., 4/-c., 354, f. 12. Monoculus polyphemus, LIN. Limulus Ameri- 

 canus, LEACH; BUCKLAND ; LAM. 



This animal is well known under the names of Horse-shoe, 

 King-crab^ and Sauce-pan fish. 



