6o A Guide to the Zoological Collections in the 



fresh- water, but the majority of which are marine. A 

 good many of the marine species are parasites and are 

 more or less degraded in form. 



The Isopoda are usually small, but one of the deep-sea 

 species — Bathynomus giganteus, two specimens of which 

 are exhibited in Case 50, is of relatively gigantic propor- 

 tions, one of the exhibited specimens being over eight 

 inches long. 



Particular attention should be paid to these magnificent 

 specimens of Bathynomus, as they exhibit on such a 

 unique scale the typical form of the body and appendages 

 of the Isopoda, showing (i) a head made up of six 

 (five) segments fused together to form a single ring and 

 bearing a pair of sessile eyes, a pair of short antennules, a 

 pair of longer antennae, a pair of mandibles, and two pairs of 

 maxillae; (2) a thorax of eight segments, the first of which, 

 bearing a pair of foot -jaws, is fused with the head, while 

 the remaining seven are separate and distinct rings, each 

 of which carries a pair of many-jointed crawling legs ; and 

 {3) an abdomen made up of seven segments, the first five 

 of which are separate and carry each a pair of broad mem- 

 branous bilobed paddles, while the last two are fused 

 together to form a broad telson with a single pair of two- 

 bladed swimming paddles : upon each lobe of each of the 

 first five pairs of abdominal appendages can be seen a 

 branching feathery gill. 



Besides Bathynomus the following Indian genera are 

 represented in the exhibited collection : — Cymothoa, Cerat- 

 othoa, Nerocila, Anilocra, Idotxa^ Cleantis, Ligia, 

 Bopyrus, and Armadillo, the last being a terrestrial 

 species. 



Bopyrus is parasitic in the gill-chamber of prawns, and 

 the males are of minute size and further attach themselves 

 as parasites to the abdomen of the female. This is well 

 seen in the two exhibited specimens, in one of which the 

 tiny male is shown alongside the female, while in the other 

 the male is seen attached in its natural position. 



