370 SYSTEMATIC PALEONTOLOGY 



lower two-tliirds; sculpture consisting of aljout 30 raised rounded radiat- 

 ing ribs with intermediate smaller ones toward the periphery of the 

 posterior end, and with rugose irregular lines of growth ; notch nearly 

 medial; interior smooth; margins of the notch thickened; the thicken- 

 ing extending nearly to the apex in a l:)elt which is slightly depressed 

 in the center; periphery slightly thickened. 



Height, 2.5 mm.; length, 6.5 mm.; width, 5.5 mm. 



Occurrence. — Choptank Formation. Greensboro. 



Collection. — Maryland Geological Survey. 



Class AMPHINEURA. 



Order POLYPLACOPHORA. 



Suborder MESOPLACOPHORA. 



Family ISCHNOCHITONID/E. 



Genus CH/ETOPLEURA Shiittleworth. 



Cli^^topleura apiculata (Say). 

 Plate LXIY, Figs, la, lb, 2a, 2b, 2c. 



Chiton apiculatus Say, 1834 (?), American Conchology, Appendix. 



Chiton transenna H. C. Lea, 1843, New Fossil Shells from the Tertiary of Virginia, 



Abst., p. 5. 

 Chiton transenna H. C. Lea, 1845, Trans. Amer. Pliilos. Soe., vol. ix, p. 246, pi. 



XXXV, fig. 35. 



Description. — " Valves eight ; dorsal triangles with series of elevated 

 points ; lateral triangles with scattered elevated points. 



" Inhabits the coast of South Carolina. 



" Whitish ; oval-oblong, convex, subcarinated ; eight-valved ; anterior 

 valve with numerous, separate, elevated, equal, sul^equidistant, points; 

 the six following valves have on their dorsal triangles from twenty to 

 thirty longitudinal series of equal, elevated, approximate rounded points ; 

 their lateral triangles with elevated points, as on the anterior valve ; pos- 

 terior valve at base like the dorsal triangles, its broad margin with the 

 points like those of the anterior valve. Length nearly half an inch." 

 Say, 1834. 



This species which is living on the Atlantic coast from Cape Cod to 



