Report op the State Geologist, 



577 



Type, Cra/nia craniolaris. Linne. 



Distribution. Lower SiluriaD to Recent (Northern Atlantic, 

 Mediterranean, Caribbean, Florida, Japan). 



Crania anomala. After Hancock. 



Fk;. ^*;g.— Dorsal surface of the animal. Fig. 267.— Ventral surface. 



mm, mesenteric muscle; di, divaricators: da, dorsal adjusters: va, ventral adjusters; oc, 

 occlusors: bm, brachial muscles; ftp, brachial process: at; alimentary canal (According to 

 Joubin, this organ should have a median, not lateral termination). 



Subgenus Ancistrocrania, Dall. 1877. 



(Plate 7, Figs. 1,8.) 

 (Synonym; Cranopsis, Dall. 1871.) 



Lower valve attached ; upper valve with two internal apophyses 

 or muscular fulcra diverging from the apex. 



Type, Ancistrocrania Parisiensis, Defrance (sp.). Cretaceous. 



Subgenus Craniscus, Dall. 1871. 

 (Plate 7, Fig. 3.) 

 i Synonym; Siphonaria, Quenstedt. 1851.) 

 Attached valve divided by a transverse and a longitudinal 

 septum into three cells, the posterior containing the muscular 

 impressions. 

 Type, Grcmiscus tiripcwtitus, Minister (sp.). Jurassic. 



\ Subgenus Pseudocrania, McCoy. 1851. 

 (Plate 7, Figs. 11-13.) 

 (Synonym; Paloeoercmia, Eichwald. 1860.) 

 Shell free ; valves convex ; margins of contact broad and Hat; 

 upper valve with three pairs of muscular scars, the largest sub- 

 marginal ; a smaller median pair, and an anterior pair with the 

 members in apposition. In the lower valve the median and 

 1891. 73 129 



