484 



MOLLUSCA 



PHYLUM VI 



the divided addiictor scar 



of the lower valve. Behind tlie anterior tliere are two 

 supplemental processes, wliich are received into the 

 sockets d' and d" of the lower valve. The species are 

 abimdant in the Middle and Upper Cretaceous, and occur 

 chiefly in littoral shallow water deposits. The most 

 noted localities are the Alps and Pyrenees, Provence, 

 Charente, Istria, Dalmatia, Greece, Sicily, Asia Minor, 

 Persia and Algiers. 



Barrettia Woodvvard. Cretaceous ; Jamaica and 

 Guatemala. 



Superfamily 7. LUCINACEA Anton (emend.). 

 „ , ,„ Shell tvith the anterior adductor scar narrower, pro- 



Htppurites cornu-vacctnum Goldi. . 7 7 77 • 7 



UpperCretaceons;Gosau,Austria. duced ventrally ; posterior scar shorter, rounded ; palhai 

 vaTv£'ko:fngVJ"ÄcW,?g l^ne simple; foot elongate, suh-clavate ; hinge feehle, teeth 



clithruni and relation of the sliell- radial, often obsolete. 

 layers. 1/2 



Family 15. Tancrediidae Fischer. 



Shell donaciform, equivalve, ivith an external ligament ; the margin of the valves 

 entire ; hinge with posterior 

 and anterior laterals, the latter 

 inconstant ; cardinals one in 

 the left and two in the right 

 valve, or two in each valve. 

 Trias to Cretaceous, (?) Eecent. 



Tancredia Lycett {Het- 

 tangia Terq.; Palaeomya Zitt. 

 and Goub.) (Figs. 787, 788). 

 Shell sub-arcuate, attenuated 

 before the beaks, wider and 

 shorter behind them ; obli- 

 quely truncate and somewhat 

 gaping posteriorly ; a cardinal tooth on each side, and also an elongated posterior 

 lateral. Trias to Cretaceous ; niaximum in Lias. 



(?) Meekia Gabb. Cretaceous ; California. (?) Hemidonax Mörch {Donacicardium 

 Vest), Recent. 



Family 16. Unicardiidae Fischer. 



Shell cordiform, equivalve, closed, concentrically striated ; adductor scars elliptical, 

 the anterior longer; pallial line simple; margin of the 

 valve smooth ; ligament external, parivincular, seated in a 

 groove ; with a grooved hinge-plate bearing a single obsolete 

 cardinal in each valve, or none. Carbon iferous to Cre- 

 taceous. 



Fig. 787. 



TaTwredia securifonnis (Dunker). Lower Lias ; 

 Hettingen, Lorraine, i/i (after Terqnern). 



Fio. 788. 



Tancredia (Falaeo- 

 viya) corallina 'Zitt. 

 and Goub. Coral- 

 Rag ; Glos, Calvados. 



Rounded, inflated. 



Fki. 789. 

 Unicardium cxcentricum d'Orb. 

 Kimmeridgian ; Cap de la Heve, 

 near Havre. i/i. 



Unicardium d'Orb. (Fig. 789). 

 with incurved beaks ; hinge margin thin, with a weak 

 cardinal tooth ; ligament deep seated. Trias to Cretaceous. 



Sealdia Ryckholt. Carboniferous. 



Pseudedmondia Fischer. Ligament comjjletely external. 

 Carboniferous. 



