406 



MOLLUSCA 



SUB-KINGDOM VI 



anterior (A) is longer and thinner than the others, which are thickened at the internal 

 end and carry a small tubercle above. In the two sub-genera, d 1 Orbignyia, Woodward 



FJG. 736. 



Hippurites radiosus, Desin. Upper Cretaceous (Dordonian) ; Royan, Charente. , Upper valve (A, Sinus of 

 the hinge ; J5, C, Grooves corresponding to anterior and posterior columns of the lower valve ; c, Anterior, and 

 c', c", Posterior processes of the clithrum). l>, Interior of lower valve seen from above (A, Sinus ; 73, C, Posi- 

 tion of anterior and posterior columns ; a, a', Adductor scars ; d, Socket of anterior, and <?.', d", of posterior 

 processes of clithrum ; , Body chamber of shell ; x, Vacant cavity near the sinus). 2/ 3 (after Bayle). 



(H. biloculus, Lam,), and Batolites, Montfort (H. organisans, Lap.), the anterior sinus 

 disappears entirely. In Pironaia, Menegh., a number of accessory folds appear behind 

 the two columns. According to Douville, the two posterior 

 columns are homologous with the smooth bands of Eadio- 

 lites, and indicate the position of the siphons. Woodward 

 supposes that the pit (x) contained the internal ligament ; 

 but so far, remains of the ligament have only been found 

 in the bottom of the outer anterior sulcus, where it seemed 

 to form a vertical band. The second adductor scar is 

 small, and located between the sulcus and the anterior 

 column (5). The clithrum of the upper valve is extremely 

 difficult to prepare, and is known in only, a few species. 

 The anterior process shows near its base two tubercles 

 (a, a'), which correspond to the divided adductor scar of 

 FIG. 737. the lower valve. Behind the anterior there are two supple- 



Hippuritescornu-vaccinum,Goidf. mental processes, which are received into the sockets d' and 



Ve P Sa?tSn ; fhr^gh "both d " of ^ lower valve - The s P ecies are ver J abundant in 

 valves showing the interlocking the Middle and Upper Cretaceous, and occur chiefly in 



clithrum and relation of the shell- *,,, -, -, ni ., m , , -, , I.,. 



layers. V 2 . 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, Woodward. Cretaceous ; Jamaica and Guatemala. 



Superfamily 7. LUCINACEA. Anton (emend.) 



Shell with the anterior adductor scar narrower, produced ventrally ; posterior scar 

 shorter, rounded ; pallial line simple ; foot elongate, sub-clavate ; hinge feeble, teeth radial, 

 often obsolete. 



