LAMELLIBRAJvrCHIATA OF THE LOWER MARLS. 129 



Conchology, Vol. Ill, p. 12, although he did not figure it. As Mr. Conrad 

 was doubtless familiar with Mr. Lea's types, which I have not seen to know 

 them as such, he was undoubtedly correct in the identification. 



Formation and locality, — In the micaceous clays below the Lower Green 

 Marls at Haddonfield, New Jersey. Borrowed from the collection of the 

 Academy of Natural Sciences of Philadelphia. 



LUCINID^. 



Geuus LUCIKA Burg. 



Lucina cretacea. 

 Plate XVIII, Figs. 23-25. 



Gyclas cretacea Conrad. ]!^ame found on label in collection. Species figured by Con- 

 rad, without name or description, in Am. Joar. Conch., Vol. Y, PL IX, Fig. 

 14, and hinge on opposite side of plate. 



Shell rather below a medium size, subcircular in outline, with the an- 

 terior and posterior cardinal margins forming a very broad angle (140^ to 

 160^) with each other; giving in some instances a nearly straight hinge- 

 line, with the rather small, pointed beaks slightly projecting beyond the 

 line, and a slight excavation in front, formed by the depression of the very 

 narrow lunule ; while behind the beaks the ligament is deeply sunken be- 

 tween the projecting shell margins. Surface of the shell marked by strong 

 lamellose concentric lines, which are rather distant, and where there has been 

 no wearing or abrasion they sometimes roll backward, and form a hollow 

 rounded concentric ridge. On the posterior side the shell is marked by a 

 rather deep constriction passing from the beak to the posterior margin just 

 behind the umbonal ridge, or sometimes giving a sunken postero-cardinal 

 area. In the interior the muscular markings are very deep and strong, and 

 the hinge-plate narrow, the right valve being characterized by a single 

 cardinal tooth, which is grooved on the surface, and by an anterior pit. 



The shell was found in the collection of the Academy of Natural Sci- 

 ences of Philadelphia with a label marked ^*Cyclas (Klein) Cretacea, 

 Conrad," apparently in Mr. Conrad's own handwriting, with the locality, 



** Haddonfield," and on the plate cited above are two figures of the shell; 

 4418 MON 9 9 



