MOLLUSCA. 619 



less the appearance of rows of discontinuous nodes, the radiating 

 furrows are much stronger and raore conspicuous upon the 

 anterior and posterior portions of. the shell, becoming fainter or 

 sometimes almost obsolete upon the central portion, the furrows 

 on the anterior part are further apart than upon the posterior 

 portion of the shell. 



Remarks. — The characteristic features of the surface markings 

 of this shell make it very easily recognizable. It occurs most 

 commonly in the form of casts of the interior and impressions 

 of the external surface, but these latter specimens almost always 

 retain the peculiar surface markings. 



Formation and locality. — Cliffwood clay, near Matawan' 

 (107); Merchantville clay-marl, near Matawan (loi), near 

 Jamesburg (140), Lenola (163); Woodbury clay, near Mata- 

 wan (103), near Haddonfield (183); Marshalltown clay-marl, 

 near Swedesboro (177) ; Wenonah sand, near Marlboro (130) ; 

 Red Bank sand. Red Bank (116). 



Geographic distribution. — New Jersey, Arkansas. 



Linearia ornatissima n. sp. 



Plate LXX., Figs. 10-12. 



Description. — Shell, small, the dimensions of the type speci- 

 men being: length, 6 mm.; height, 4.3 mm.; nearly equilateral, 

 broadly subtriangular in outline with the basal angles rounded; 

 beak central; the cardinal margins meeting at the beak in an 

 angle of about 120°, anterior and posterior margins subequally 

 rounded, their greatest extension below the mid-height of the 

 shell; ventral margin gently convex. Valves depressed convex, 

 most prominent on the umbo, the surface sloping abruptly to 

 the cardinal margins and gently to the lateral and basal margins. 

 Surface marked by strong radiating ribs anteriorly and pos- 

 teriorly, which gradually become fainter towards the median 

 portion of the ventral margin ; on the umbo and on an area ex- 

 tending ventrally from the umbo nearly to the basal margin, the 

 shell is smooth ; the anterior and posterior ribs do not continue 

 to the beak but disappear along the margins of the central smooth 



