502 CRETACEOUS PALEONTOLOGY. 



mens, which are perfectly preserved up to^ the beak, is any per- 

 foration shown in the convex valve, but in several of those 

 which become concave towards the front there is apparently a 

 broad perforation close tO' the beak, although there is some rea- 

 son for doubting the presence of an actual perforation in this 

 valve, as it seems to be absent from some specimens which 

 are complete toi the beak. 



There seenns tO' be no sufficient reason for recognizing the 

 two' species of Paramomia of Whitfield's monograph. The type 

 of Morton's species, P. scabra, illustrated by Whitfield, is only 

 a fragment of a shell belonging to the same species as the one 

 illustrated as P. Imeata, although it is somewhat more irregular 

 and rougher than usual. Morton's name having priority is 

 adopted for the species. P. saifordi Con., from Tennessee, must 

 also be considered as a synonym. 



Formation and locality. — Merchantville clay-marl, Lenola 

 (163); Marshalltown clay-marl, near Swedesboro (177, 179); 

 Navesink marl, Crosswicks Creek (147*, 19.5). 



Geographic distribution. — New Jersey, Alabama, Mississippi, 

 Tennessee. 



Super-family MYTILACEA. 



Family MYTILIDAE. 



Genus Mythus Linneus. 



Mytilus smocki n. sp. 



Plate LV., Figs. 1-4. 



Description. — Shell more or less arcuate, the larger type speci- 

 men with an extreme length of 37 mm., a maximum width of 

 13 mm., and thickness of both valves 18 mm. The valves 

 strongly convex, with a rounded ridge below the middle extend- 

 ing from the beak to the postero-basal margin, below the 

 ridge the surface of the valves are rather abruptly inflected, 

 meeting nearly in a plane along the ventral margin. The beaks 

 pointed, the dorsal and ventral margins diverging at an angle 

 of about 35°; the hinge arcuate, passing gradually into the pos- 



