LAMKLIJBKANCHIATA. 



121 



No. 333. Megalodon cuculatus. Sow. 



This specimen belongs to the family Megalodontidae, char- 

 acterized by a somewhat regular, ovoid, equi valve shell, with 

 from one to three cardinal teeth and two muscular impres- 

 sions. Fourteen fossil species are known from the Upper 

 Silurian and Devonian. From the Lower Devonian, Cologne, 

 Rhenish Prussia. 



No. 334. Crassatella protexta, <?ou. 



This genus has the ligament internal. It commences in the Cretaceous and 

 abounds to-day, and is the type of a family. Eocene,' Claiborne, Alabama. 



No. 335. Astarte obliqua, Desh. 



This genus is to-day represented by twenty species, widely distributed in 

 the Northern seas; 285 fossil species are known, beginning with the Carbon- 

 iferous. Family Astartidse. Lower Oolite, Bayeux, Calvados, France. 



No. 336. Venericardia rotunda, "Lea. 



This belongs to the family Astartidte, and the genus dates from the Creta- 

 ceous. Eocene, Claiborne, Alabama. 



No. 337. Cardita Partschii, Goldf. 

 Miocene, Steinabrunn, Austria. 



No. 328. Opis lunulata, Sow. 



Confined to, and characteristic of the Mesozoic; 43 species are known. 

 Lower Oolite, Feuguerolles, Calvados, France. 



ORDER ASIPHONIDA. 



No. 329. Trigonia costata, Park. 



This belongs to the Trigonidte, the shell of which is 

 equivalve and trigonal, with the umbones directed pos- 

 teriorly; 100 fossil species are known, dating from the 

 Devonian, but only three living forms. From the Lower 

 Oolite, OEschingen, Wurtemberg. 



No. 330. Trigonia incurva, Sow. 



From the Upper Oolite, Swindon Wilts, England. 



