730 CRETACEOUS PALEONTOLOGY. 



Super-family RACHIGLOSSA. 

 Family BUOOINIDAE. 



Genus PERISSOLAX Gabb. 

 Perissolax dubia (Gabb). 



Plate LXXXV., Figs. 1-5. 



1860. Purpuroides ? dubia Gabb, Proc. Acad. Nat. Sci. Phil. 



(1860), p. 94, pi. 2, fig. ii. 



1861. Purpuroidea ? dubia Gabb, Synop. Moll. Cret. Form., p. 



129 (73). 

 1864: Purpuroidea ? dubia Meek, Check List Inv. Foss. N. A., 



Cret. and Jur., p. 21. 



1868. Purpuroidea ? dubia Con., Cook's Geol. N. J., p. 730. 

 1892. Perissolax dubia Whitf., Pal. N. J., vol. 2 (Monog. U. S. 



G. S., vol. 1 8), p. 47, pi. 3, figs. 9-1 1. 

 1892. Tritonida obesa Whitf., Pal. N. J., vol. 2 (Monog. U. S. 



G. S., vol. 18), p. 79, pi. 9, figs. 1-3. 

 1905. Perissolax dubia Johns., Proc. Acad. Nat. Sci. Phil. 



(1905), p. 24. 



Description. "Shell of medium size, conical above, abruptly 

 contracted below the largest part of the last volution, and ex- 

 tended in front into a short, somewhat slender beak ; volutions 

 about four, strong, convex on the surface, with well-marked 

 sutures ; apical angle in the vicinity of 50 ; aperture ovate, 

 somewhat acute at each end but prolonged below; surface 

 marked by revolving ridges and by closely arranged vertical folds ; 

 of the former, there are n, eight of which may be said to be 

 above the middle of the volution, or above the peripherry, while 

 three only are really below this point, and these more distant and 

 somewhat stronger than the others, with distinctly concave spaces 

 between, while the lower half of the space between the beak and 

 the periphery seems to be destitute of ridges ; vertical folds low 

 and rounded, with concave interspaces of about an equal breadth 

 with the folds, or the folds may be said to unite at their bases, 

 occupying the entire space; 12 of them can be counted on the 



