100 



is narrow in the flat cuirass , and triangular in 

 the triangular cuirass of the Desmidium Sicartxii 

 (PI. IV. fig. 44.). The form of the bivalve cuirass 

 is always analogous to that of the animalcule. Suri- 

 rellae (for ex. the Surirella Venus (fig. 1 4.) have, 

 according to the length of the animalcule , an open 

 cuirass, each valve of which is like a pot, the one 

 included in the other, in a very peculiar manner, 

 forming a sort of inge (fig. 4. b.), nearly similar to 

 a round snuff-box. Their edges, besides, are supplied 

 with rounded and radiated elevations (fig. 4. A.), 

 between which are seen furrows of the same size 

 (fig. 4. B.). Though different, the bivalve cuirass 

 of the Closteria has an analogous form. Each valve 

 (fig. 61. A. A.) forms cornucopiae, the uniting point 

 of which is seen in the middle of the animalcule, 

 where the sexual openings (fig. 61. c.) are to be found. 

 No inge is to be seen , but the two thin edges of 

 the valves (fig. 62. d.) are placed immediately one 

 upon the other. This cuirass is open at each point 

 of a valvule , its being the place \vhere we see the 

 opening which I consider as the mouth (fig. 61. 63. 

 b. b. 64. 65. a. a.) 



In the Pleurosicyos myriopodus , the cuirass has 

 two valves , of the same form as in the Closteria. 

 It is, besides, octangular (fig. 69.), and on each side 

 of an angle, 8 12 pedal holes (fig. 68. b.) are seen. 

 The Cosmaria must be considered as double ani- 

 mals, forming together a double cuirass, and each 

 separately a single one. 



