MOLLUSCA. 573 



and no laterals. Muscular impressions rather large but not 

 deeply impressed, pallial line with a deep, narrow, acutely sub- 

 angular sinus, whose inner extremity is directed towards a point 

 between the beak and the anterior muscular impression. Sur- 

 face of the shell nearly smooth, marked only by fine lines of 

 growth. 



Re-marks. — The type specimens of Lucina pinguis Con. and 

 Mysia gibbosa Gabb, are certainly members of the same species, 

 but that of Mysia parilis Con., seems to be a distinct form, al- 

 though it has frequently been considered as a synonym of the 

 others. Both species are here referred to the genus Tenea. T. 

 pinguis has not been observed to grow as large as T. parilis; it 

 is much more gibbous, the entire shell being almost globular in 

 form, and it seems to have been marked with stronger concentric 

 lines of growth. The only authentic examples. of the species 

 seem to have come from the Navesink marl, while T. parilis occurs 

 in the lower formations, although it has also been observed in 

 the Red Bank ,^and. Whitfield's type of Dosinia gabbi is a good 

 typical example of the form here considered as T. parilis, and 

 one of the specimens he has illustrated as T. pinguis is also a 

 typical representative of this species, although somewhat more 

 ovate than usual. The hinge characters have not been observed 

 in any of the examples in the recent collections of the Survey, 

 but the specimen upon which the genus Tenea was established 

 came from the Woodbury clay near Haddonfield where the fauna 

 is essentially like that at Lorillard. The specimens of T. parilis 

 from Lorillard are much larger than the type of the species, but 

 there are specimens of the species in the National Museum from 

 the typical locality in Tippah County, Mississippi, which are much 

 larger than the type. Considerable individual variation is ex- 

 hibited among different examples of the species, the more usual 

 form is subcircular or obscurely subquadrangular, but occasion- 

 ally one is met with which is more nearly subovate in outline. 

 Many of the southern examples of the species retain the shell 

 itself, which is very thin and marked only by fine, concentric lines 

 of growth. 



Formation and locality.— QWHwood clay, Cliffwood Point, 

 (105) ; Merchantville clay-marl, near Jamesburg (141), Lenola 



