BRACHIOPODA. 377 
Arthropomata.l 
than one-half the size attained by this species as found at Middleville, New York, 
and since they are constantly smaller, the varietal name minor is here applied to 
them. The growth lines are conspicuous in some specimens, while in others they 
are nearly obsolete. The muscular markings are undefined, owing to the tenuity of 
the valves. 
Formation and locality.— 'Not uncommon near the base of the Galena shales at St. Paul; associated 
with Clitambonites, three miles south of Cannon Falls and at Kenyon, Minnesota. Also in the upper part 
of the Trenton shales at Chatfleld. 
Collectors.— A. D. Meeds and C. Schuchert. 
Mus. Reg. No. 7279. 
Subclass ARTHROPOMATA, Owen. 
Order PROTREMATA, Beecher. 
Family CLITAMBONITID.E, n. fam:'' 
Genus CLITAMBONITES, Pander. 
1830. Klitambonites, Pander. Beitrage zur Geognosie des russlschen Reiches, p. 70. 
1892. Clitambonites, Hall. Palaeontology of New York, vol. viii, pt. i, p. 233. 
Orthisina, d'ORBiGNY (1847) and subsequent authors. 
Description: "Shells with a subsemicircular marginal outline; convex or sub* 
pyramidal in the typical group. Hinge-line straight and forming the greatest 
diameter of the shell. Pedicle [ventral] valve elevated, cardinal area high, vertical, 
or sometimes incurved and crossed by a broad delthyrium, which is normally covered 
by a convex, perforate deltidium. On the interior of the valve the dental lamellas 
are very strongly developed, converging and uniting in the median line before 
reaching the bottom of the valve, thus forming a spondylium, which with the del- 
tidium encloses a conical subrostral vault. This plate is supported by a median 
septum extending for about one-half the length of the valve. [Adductor, diductor 
and adjustor scars occupy the upper surface of the spondylium.] In the brachial 
[dorsal] valve the cardinal area is considerably developed and the delthyrium filled 
by a conspicuous callosity, against the inner side of which the simple orthoid cardinal 
process abuts. The dental sockets are large, the crural plates low and continuous 
with the edges of the delthyrial callosity. A thickened transverse area is formed 
in the umbonal region by the union of the inner portions of the crural plates with 
the cardinal process, and thence a broad median ridge is continued forward through 
the muscular area, which is sharply defined and quadripartite. External surface 
covered with radiating striae. Shell substance impunctate. 
*This family will contain Protorthis. Ua.\\, Clitambonites, Pander. Hemt'pronftes, Pander, and Scenidium. Hall. Waagen 
(Pal. Indica, vol i, p. 576, 1884,) proposed the sub-family Orthisince for the genus Orthisina. D'Orbijiuy's family Orthisidce 
contains Stroptiomena, Orthis, and Orthisina=Clitambonites, genera now referred to three distinct families. 
