BRACHTOPODA. 381 
OUtaiiiboiiItes dlvcrsa, var. altlsslina.] 
Clitambonites diversa, var. altissima, n. var. 
PLATE XXX, FIGS. 18 and I'J. 
1892. Clitambonites americanus var. Hall. Palasontology of Now York, vol. viii, pi. xvA, (l^s. 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.— Sii\'Gra\ specimens of this variety have been found by Mr. W. II. Scofleld 
associated with C. diversa in the Galena shales south of Cannon Falls, Minnesota. 
Genus SCENIDIUM, Hall. 
I860. Skenidium, IlALL. Thirteenth Report N. Y. State Cabinet of Natural History, p. 70. 
. 1892. Scenidium, Hall. Palajontology 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 extremity. 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 Clitamhonitidce. 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 (undeflned). 
1892. Skenidium anthonensis Sakdeson. Bulletin of the Minnesota Academy of Natural Sciences, 
vol. iii, p. 333, pi. iv, tig. 7. 
1892. Scenidium halli Hall. Paki'ontology of New Y'ork, vol. viii, pt. i, p. 242, pi. viiA, Ilgs. 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- 
