134 NATURAL HISTORY 



307. Trichoda hjnceus. (Aspidisca, E.) — This ani- 

 malcule is nearly circular, flat, and covered with a de- 

 licate shell ; it resembles in miniature the round Lyn- 

 ceus, drawn and described in the " Microscopic Cabinet/' 

 having, like it, a sharp pointed rostrum or beak, with a 

 cluster of delicate hairs beneath it ; the margin of the 

 opposite end is furnished with bristles. Size, l-900th of 

 an inch. 



308. Trichoda charon {Euploea, E.) — The charon 

 boat-shaped Trichoda has a strong resemblance in its ex- 

 ternal characters to the animals of the class Entomos- 

 tracea, and, like the genera Amymone and Nauphius*, 

 its back is protected by a shell. This crustaceous shield 

 is very thin, and so transparent that when the water is 

 clear it is scarcely perceptible. Figures 182 to 186 re- 

 present various views of it. The form of the shell 

 varies in different specimens : the most general shape I 

 have observed is shewn at figure 182, one side overlapping 

 more than the other. It usually swims on its back, in 

 which position the bristles on each side of the body, and 

 the cluster towards each extremity, can be seen : the 

 side bristles mostly appear vibrating, in this situation of 

 the animal ; even when it is stationary they produce a 

 current in the water, probably for the purpose of bring- 

 ing a fresh portion for respiration. The mouth is situ- 

 ated at the side, near the row of cilia ; it is a longi- 

 tudinal aperture, commencing near the apex of the 



* See " Microscopic Cabinet," page 84. 



