SUPER-ORDKH III 



OSTHACODA 



64fl 



Cythere, Miiller (Figs. 1342, 1343). Sh.-ll ivnil'..nn or sub- quadrat.-, n-u;illy 

 widest in front ; sui -fa. A 



ornamented with punctae, 

 nodes, spines, and ridges ; 

 hinge teeth strong, placed 

 one at each end of a Imri- 

 xontal bar wliicli fits into a 

 corresponding furrow and 

 sockets of the left valve. 

 In the sub-genus Cythereis, 

 Jones (Fig. 1344), the con- 

 necting bar of the hinge is 

 wanting. Cretaceous to 

 Recent. 



Cytheridea, Bosq. (Fig. 

 1345). Differs from Cythere in having hinge beset with row of small teeth in right 



Fl<;. 134'-'. 



Cyt)i- . KIM-HI. s|,. 



Miocene; Leognan, nwir Hor- 

 cleaux. -"-Y! (after Bosqu.-t). 



1343. 



nrian. 



.lor.l:ili Hi;: 



laml. .1. Int'-rior of left valve. 



/;, Exterior of ri-ht valve, en- 

 larged (aftr Bra-ly). 





FIG. 1344. 

 Cythereis quadrilatera, Roemer. Gault ; Folkestone. <25 /i (after T. Rupert Jones). 



valve, often interrupted in the middle, and with corresponding pits in the left. Jura 

 to Recent. 



Cytherideis, Jones. Shell more or less triangular. Surface 

 smooth, pitted or tuberculate ; hinge simple. Cretaceous to 

 Recent. 



Family 4. Thlipsuridae. Jones. 



Minute, reniform, or ovate inequivalve shells, the margin of one 

 FIG. 1345. valve overlapping that of the other more or less completely ; dorsal 



"Bocemr mar 9^ n arcuate, ventral sometimes straight or slightly sinuate. 

 Coiweii Bay, England. Surface with two or more definite pits. 

 22/! (after Jones). 



Thlipsura, Jones and Holl. Each valve generally witli three 

 pits, one posterior and two in the anterior half. No ornament. Silurian. 



Octonaria, Jones. Differs from the last in having the surface of valves raised into 

 a thin spiral or annular ridge which in more typical forms is 8 -shaped. Silurian and 

 Devonian. 



Phreatura, Jones and K. Distinguished from Thlipsura by the strong compression 

 of posterior end of shell, which is further marked by a shallow semicircular pit ; a 

 similar but smaller pit present at anterior extremity. Carboniferous. 



Family 5. Cypridae. Zenker. 



Minute, mostly reniform or elongate-ovate, corneous or corneo-calcareous shells, with 

 thin, somewhat unequal valves, one overlapping the other either ventrally or dorsally or 

 loth. 



Recent Cypridae are chiefly fresh-water inhabitants, but this is true in a leaser 

 degree of the fossil forms. All the Palaeozoic representatives are marine, excepting 



