344 



ARTHEOPODA. 



genus ranges from the Silurian to the Carboniferous. Isochilina 

 (fig. 201, B) nearly resembles the preceding, but the valves 

 are equal. It is not uncommon in the Silurian. Aristozoe, 



Fig. 201. Types of Ostracoda. A, Aristozoe memoranda, of the natural size Silurian ; 

 B, Isochilina Ottawa, enlarged four times (left valve and ventral view) Silurian ; c, Leper- 

 ditia Josephiana, of the natural size (right valve and anterior view) Silurian ; D, Leperditia 

 solilaria, enlarged, showing the eye-spot and muscular impression Silurian ; E, Primitia 

 strangulata Silurian ; r, Outline of the same, enlarged ; o, Right and left valves of Primi- 

 tia, tarda Silurian ; H, Beyrichia complicata Silurian ; i, Beyrichia oculifera, showing the 

 elevated eye-spot, greatly enlarged Silurian ; J, Entomis pelagica, right valve, enlarged 

 twice Silurian ; K, Entomis impendens, enlarged Silurian ; L, Cypridina Wrightiana, 

 left valve, enlarged four times Carboniferous ; M, Dorsal view of a small example of 

 Entomoconchus Scouleri, enlarged four times Carboniferous ; N, Left valve of Polycope 

 simplex, enlarged eight times Carboniferous ; o, Cypris Browniana, viewed dorsally, en- 

 larged twenty-five times Pleistocene ; P, Candona Candida, viewed ventrally, and similarly 

 enlarged Pleistocene ; Q, Cythere punctata, right valve, similarly enlarged Pliocene ; R, 

 Interior of left valve of the same. (After Barrande, Rupert Jones, M'Coy, Hall, and G. S. 

 Brady.) 



(fig. 201, A), Orozoe, and Callizoe are Silurian genera allied 

 to Leper ditia, but they have tubercular eminences developed 



