ORDER I 



PRIONODESMACEA 



881 



cannot properly be regarded as of generic value. The most familiar of the groups tlm> 

 named an- as In Hows : 



Chlamys, Bolten (Pallium, Schum. ; Decadopccten, Riipp.), (Figs. 661, 6i'J . Sln-11 



Fi... (;.;.. 



Pecten 



Pliocene; Rhodes. 



hinn. 



i'n (< ', i ,n ptoHtctes) lens, 

 Sow. Mi.ldhs Jura; Balin, 

 near Cracow. 1/1- 



Fie. 604. 



/'. (Knt-li 



oormttoc, 



UppiT -I 



henzollern. 1/1- 



radially sculptured, nearly equivalve, with small, unequal ears, and deep byssal notch with 

 well-developed ctenolium. Trias to Recent. 



Camptonectes, Ag. (Fig. 663). Shell small, thin, nearly smooth, with fine divergent 

 striation radiating from a median line. Jura to Recent. 



Entolium, Meek (Fig. 664). Smooth, thin, with sub-equal ears diverging at a sharp angh- 

 above the beaks ; byssal notch obsolete. Carboniferous to Cretaceous. 



Pseudamusium, Adams. Shell small, thin, glassy ; the posterior ear obsolete, byssal notch 

 distinct. Cretaceous to Recent. Syncyclonema, Meek is scarcely different. 



Fin. 665. 

 Amusium cristatus, Bronn sp. Miocene ; Baden, near Vienna. 1/1- 



Fi... 



llin,iit,.i>,j,,-t,i.-, I'liill. si.. 

 Mi.l.ll.- Junt; Balin, near 

 Cracow. 1/1. 



Amusium, Schum. (Fig. 665). Shell \\iili i-aJM-d r.-nlial ril>h-t> intiTii.-illy: i-xti-ni;ill\ 

 smooth or delicately sculptured ; valves large, flatti*h, with sub-equal car> : l.y>sil notch 

 incouspicuoiLs or absent. Lias to Recent. 



Sub-genus : Propcamusium, Greg. Small, thin, abyssal ; often with relatively conspicuous 

 sculpture, usually discrepant on the valves. Tertiary and Recent. 



Hinnites, Defr. (Fig. 666). Shell free and Pectiiiiform wlu-n youn^, later ndln-ivni 

 to other objects and more or less distorted. Trias to Recent. 



Pedum, Brug. Shell with an alivincular ligament in an open groove and aiva lik-- 

 that of Spondylus in the adult ; the young like Chlamys. Recent ; sessile in corals. 



Family 34. Spondylidae. Fleming. 



Shell ineqiwvalve, nearly equilateral, closed, Pectiniform, obscurely auriculate, mono- 

 myarian; sessile; area amphidetic, much larger on the attached valve; ligament alivincular, 

 resilium more or less submerged; byssus obsolete; hinge with a Taxodont province !n m. 



