NO. 1395. CAMBRIAN BRACHIOPODA-WALCOTT. 267 



PLECTORTHIS NEWTONENSIS Weller. 



Orthix iiewtonenm WEhhER, Geol. Sur. New Jersey, Pal., Ill, l!t03. Pal. Faunas, 

 p. 113, pi. I, figs. 3-5. 



This little shell occurs in the form of casts in a sandstone that is too 

 coarse to preserve the details of the outer surface. The cast of the 

 interior shows tine, simple, radiating ribs that increase by interpola- 

 tion and that are coarser on the ventral than on the dorsal valve. 

 Ventral valve slightly flattened at the front; dorsal valve with a broad 

 mesial sinus. The shell appears to have been thin. The cast of the 

 pseudospondylium of the ventral valve shows it to have been clearly 

 defined; the area is low and not sharply defined from the curve of the 

 cardinal margin; it is nearly vertical to the plane of the margin of the 

 valve. The cast of the area beneath the umbo in the dorsal valve is 

 more triangular and less transverse than usually occurs; unfortunately 

 the material is too imperfect to determine any details. 



This species is the eastern representative in the Upper Cam])rian of 

 Plectorthis indianola and Iddingsi. As far as can be determined by 

 the material available for comparison, it is closely related to them, but 

 it is not probable that they are specifically identical. 



Ffyrmation and locality. — Upper Cambrian sandstone, Hardyston 

 (|uartzite of Weller, Newton, New Jersey. 



PLECTORTHIS PAGODA, new species. 



Shell transverse, subsemicircular; a ventral valve 11 mm. in length 

 has a width of 15 mm., and a dorsal valve 8 mm. in length has a 

 width of 13 mm. ; hinge line a little shorter than the greatest width of 

 the shell; cardinal angles vary from 75° to 111*^; valves moderately 

 convex. Cardinal area narrow in both valves and inclined backward 

 from the hinge line. Surface marked by equidistant, narrow, low 

 ribs, 3 in a space of 2 mm. near the front margin of a shell 1(1 mm. 

 long, with fine, radiating stria? between them; the radiating ribs and 

 striffi are crossed by fine, concentric stria?, and lines of growth. 



Ventral valve with a strong, somewhat angular, median fold, rising 

 from a well defined depression on each side of it, or it might be 

 designated as a very sti"ong rib rising above the general surface of 

 the valve from a broad, median depression: the lateral slopes are 

 gently convex. Dorsal valve with a strong, angular, median depres- 

 sion, beginning at the posterior margin and gradually widening to the 

 front; the sides of the depression rise above the general surface of the 

 valve, and form with the outer sloyje a well defined, low ridge on each 

 side that extends a little forward on the front margin to fit into the 

 depressions on each side of the median fold of the ventral valve. 



The interior of a small dorsal valve has a broad, strong median ridge 

 corresponding to the depression on the exterior surface; a main vascular 



