CLARS I 



PELECYPODA 

 Superfamily 8. ANOMIACEA Herrmannsen. 



4G1 



Shell monomyarian, not alate ; edentulous or isodont, usually sessile ; shell substance 

 nacreous, tuhidiferous, ivith traces of a prismatic layer ; area ohscure, usually small, 

 amphidetic ; ligament ohscure, ivith an alivincular internal resilium ; (jills filibranchiate, 

 mantle lohes free ; foot small, grooved, digitiform ; dioecious ; marine. 



Family 37. Anomiidae Gray. 



Shell variable, irregulär and inequivalve when sessile, byssiferous vjhen young ; in 

 most genera the hyssus becomes modified to a calcißed or horny flug ^Kissing through 

 a foramen in the right valve, and fastened to other ohjects, a condition which may he 

 permanent or transient ; area small, amphidetic ; ligament amphidetic, more or less 

 internal, supplemented by an internal resilium, for which the crura serve as chondrophores, 

 ali- or multivincular ; hinge usually edentulous, rarely rugose, with amorphous inter- 

 loching rugosities ; posterior adductor small, sub-central, in the sessile forms reinforced by 

 the pedo-byssal muscles, which are modified for Service as adductors. (?) Devonian. Jura 

 to Kecent. 



Anomia Müll. Shell thin, sessile by tlie calcified byssus passing through a siiiiis 

 or Perforation in the right valve, conforming to the subjacent surfece ; the left valve 

 more convex, with four miiscular scars on 

 a central area ; a chondrophore in the 

 lower valve. Jura to Eecent. 



(?) Limanomia Bouch. Devonian. 

 Hypotrema d'Orb. Jura and Cretaceous. 

 Placunanomia Brod. Miocene to Recent. 



Garolia Cantraine. (Fig. 725). Shell 

 orbicular, compressed, radially striated ; 

 right valve with a byssal foramen nearly 

 closed in the adult ; resilium much as in 

 Anomia ; adductor scar single. Eocene ; 

 Egypt. 



Subgenus : Wakullina Dali. Smooth ; 

 byssal foramen obsolete ; the resilium received 

 on diverging crura on the upper valve. Oligo- 

 cene ; Florida. 



Placenta Retzius {Placuna Brug. ; 

 Placunema Stob; Pseudoplacuna Mayer). 

 Shell free, orbicular, thin, very compressed ; 

 the resilium with long, unequal crura. 

 Tertiary and Recent. 



Ephippium Bolten. Like Placenta, 

 but the Shell radially waved ; young with a small byssal Perforation, which becomes 

 closed and obsolete in the adult. Tertiary and Recent. 



Placunopsis Morr. and Lyc. Shell rounded, imperforate, free, or sessile. Jura. 



Hemiplicatula Desh. {Semiplicatula Fisch.) ; Saintia Raine. Eocene. Paranomia 

 Conrad. Ripley Group. Monia Gray. Miocene to Recent ; California. 



Section E. Dysodonta Neumayr (emend.). 

 Superfamily 9. MYTILACEA Färussac. 



Shell anisomyarian, usually equivalve, not alate or notched for a hyssus, edentulous or 

 dysodont ; shell substance sub-nacreous, rarely more or less prismatic, with a rom^icuons 



Fic. 725. 



Carolia placunoides Cantr. Eocene ; Wadi el Tih, near 



Cairo, Egypt. Interior of both valves, 2/3. 



