BRACHIOPODA. 381 



Clltambonites dlver'sa, var. altissima.l 



CLITAMBONITES DIVERSA, var. ALTISSIMA, n. var. 



PLATE XXX, FIGS. 18 and 19. 



1892. Clitambonites americanus var. HALL. Paleontology of New York, vol. viii, pi. xvA, flgs. 7, 8. 



This variety is readily distinguished by the exceeding elevation of the cardinal 

 area of the ventral valve. This feature is so striking that its recognition seems to 

 be demanded. 



Formation and locality. Several specimens of this variety have been found by Mr. W. H. Scofleld 

 associated with C. diversa in the Galena shales south of Cannon Falls, Minnesota. 



Genus SCENIDIUM, Hall. 



I860. Skenidium, HALL. Thirteenth Report N. Y. State Cabinet of Natural History, p. 70. 

 1892. Scenidium, HALL. Palaeontology of New York, vol. viii, pt. i, p. 241. 



Description: "Shell subpyramidal, somewhat semicircular, with or without 

 median sinus and elevation. Area large, triangular, divided by a narrow fissure, 

 which is sometimes closed at the summit by a concave deltidium [spondyliumj. Valves 

 articulating by teeth and sockets, which are often obscure or obsolete. Dorsal valve 

 flat, or varying from depressed-convex to concave. Beak entire, or indented by the 

 foramen; cardinal line straight and usually equalling the width of the shell; cardinal 

 plates broad and well developed, marked by the imprints of the peduncular muscles, 

 and produced in the middle in a pointed process; the cardinal process extends, as a 

 median septum, through the length of the shell, and may be simple or divided at its 

 anterior extrepiity. Ventral valve elevated, subpyramidal; beak straight or slightly 

 arched; muscular impressions undetermined. Exterior surface covered with radi- 

 ating striae." (Hall, 1892, op. cit.) 



Type: Orthis insignis Hall. 



The ancestral stock from which Scenidium was developed is very uncertain, 

 though it seems to have had its origin in the Clitambonitidce. The genus appears in 

 the Trenton, but it is not until the Lower Helderberg formation is reached that 

 the greatest development of its generic character is attained. It is also known in 

 the Middle Devonian of Europe. 



SCENIDIUM ANTHONENSIS Sardeson. 



PLATE XXX. FIGS. 20-23 



1869. Skenidium halli SAFFORD. Geology of Tennessee, p. 287 (undefined). 



1892. Skenidium anthonensis SARDESON. Bulletin of the Minnesota Academy of Natural Sciences, 



vol. iii, p. 333, pl.iv, flg. 7. 

 1892. Scenidium halli HALL. Paleontology of New York, vol. viii, pt. i, p. 242, pi. vnA, flgs. 33-39. 



In its external characters this little species is much like the young of Orthis 

 tricenaria, but the concentric growth lines show it to be an adult form. The hinge- 



