nUACHIOI'ODA. 



117 



Animal: — Mnntle exti-ndiiifi to tin- ninrfrin of the valves, 

 closely adherent ; ornl arms eloiifrated, folded upon tlieinselves, 

 frinired witli l()ii<; rirri on tiieir onter niarj^ins, and sujiported hy 

 a cuniplicated shelly loop (fig. 2(1). 



Craniaeea' (part.), Mnike, Syii. ed. 1. p. .Of), 18l'S. 

 Craniaeea (part.), Menke, Syii. ed. 2. p. !^(), l8.'j(). 

 Crania- (Les Cninies), part., F&tuss. 'I'ahl. Syst. p. 38, 1821. 

 Theeideidje, Grny, Syn. B. M. 18-12, 85. 92. 

 Theeidieiihe, Kinr/, Permian Fosxi/s, 81. 142. 

 Theeidiic, ITOrhigny, Ann. Sci. Nat. 1848. 

 Cr}])tol)mehia. Gray, Ann. Nat. Hist. 1848, vii. p. 4.35. 

 AnevIol)racliia {])art.). King, Permian Fossil.s, 81. 142. 

 Theiidea- (Theeidees), Desk. Ency. Me'th. iii. t. , 1836. 

 Thccidioda;, Agassiz, Nomen. 1847. 



1. TUECIDIUM. 

 Char, of Fam. 



Thecidium pumilum. 



Fig. 24. Fig. 25. 



Fig. 24. Dorsal valve -.—j. cardinal process. 



Fig. 25. Ventral valve:—/, foramen (closed); rf. deltidium ; t. teeth; a. ad- 

 ductor impreggions ; r. retractors ; p. pedicel-muscles. 



