64 y^ Guide to the Zoological Collections in the 



ing the gills and giving up its oxygen, passes out at the 

 fore end of the chamber, a continuous current from behind 

 forwards being kept up not merely by the movements of 

 the legs but by a special " baling-out scoop " or scapho- 

 gnathite, attached to the second pair of maxillse. Similar 

 baling and sweeping organs are often attached to the 

 maxillipeds, as is well seen in the disarticulated specimen 

 of the crab Scylla serrata. The nature and arrangement 

 of the gills as well as of the digestive system, of the 

 circulatory system (heart, etc.), and of the nervous system, 

 should be observed in the dissected spirit specimens 

 of Scylla, Palaemon, Palinurus, Pendens and Nephropsis, 

 in Case 54, in which is also shown the stomach of a large 

 crab laid open to display the gastric teeth and gastr'" 

 hairs. 



a, DECAPODA MACRURA. 



[Qrit0cs 37-41, 49. 53. 55]. 



This sub-Order includes the Shrimps, Prawns, Lobsters, 

 Crayfish, etc. 



For a general idea of the structure of a typical macrur- 

 ous or long-tailed Decapod Crustacean, the disarticulated 

 specimen of one of the common Indian prawns {Penscus 

 indicus) in Case 49 should be studied. 



Comparing this with the specimen of the common 

 Indian edible crab {Scylla serrata) alongside, we find 

 that the Prawn differs from the Crab in having a long and 

 large abdomen or " tail ", every segment of which, except 

 the last, carries a pair of swimming-legs, and that the legs 

 of the last segment but one are expanded to form with 

 the last and legless segment a powerful fin or " swim- 

 meret." 



Other differences easy to notice are that the third pair 

 of foot-jaws or maxillipeds in the Prawn are slender and 

 claw-like, and that the carapace is prolonged anteriorly 

 into a long pointed "rostrum." 



