PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 383 
shallow and wide to a point just anterior to the middle where the sulcus dies out 
and the valve is evenly convex; sulcus occupied by Io to 12 costellae. 
Shell too imperfect for measurement. 
Figured specimens.—116950, 116951. 
Horizon and locality —Little Oak formation in Alabama: On U. S. Highway 
31, 3 mile north of the bridge at Pelham, Bessemer Iron District (15’) Quad- 
rangle; Bailey Gap road junction with main Cahaba Valley road, SW4SW3 sec. 
13, T. 19 S., R. 2 W., 1} miles northeast of Newhope Church, Vandiver (15’) 
Quadrangle. 
Discussion.—Two specimens answering to the above description occur in the 
collection. These shells are obviously related to G. concinnula but appear to be 
more finely costellated. They may be variations of the common Little Oak species. 
GLYPTORTHIS sp. 4 
Plate 46, G, figures 41, 42 
Shell small for the genus, wider than long; hinge about equal to the midwidth; 
sides rounded; anterior commissure rectimarginate to faintly sulcate; valves 
marked by 16 to 18 costellae. 
Pedicle valve gently convex in lateral profile, gently convex in anterior profile 
but with the median region somewhat narrowly swollen; median costella promi- 
nent and forming a low fold; flanks gently swollen. 
Brachial valve gently convex in both profiles; sulcus originating at umbo 
widening to the anterior margin, occupied by 3 or 4 costellae; flanks gently swol- 
len; interior with thin cardinal process, somewhat thickened notothyrial platform, 
and stout brachiophores. 
Measurements in mm.—116952a, length 2.8, brachial length 2.7, width 3.6, 
hinge width 3.5, thickness 1.3. 
Figured specimen.—116952a. 
Horizon and locality—McLish formation (zone 45) in Oklahoma: On West 
Spring Creek, sec. 6, T. 2 S., R. 1 W., Murray County. 
Discussion.—The specimens of this species in the National Collection are all 
small and somewhat variable. They have some characters of young specimens 
of Glyptorthis. A larger collection is needed to make certain whether or not the 
adult character is one of small size. The species at present cannot be related to 
any known one from Oklahoma. 
Genus ERIDORTHIS Foerste, 1909 
Eridorthis Forrste, Bull. Sci. Lab., Denison Univ., vol. 14, p. 223, 1909.—ScHUCHERT and 
Coorer, Mem. Peabody Mus. Nat. Hist., vol. 4, pt. 1, p. 91, 1932. 
This unusual genus which is undoubtedly an offshoot from the main stem of 
Glyptorthis, is characterized by a strong development of the fold and sulcus. 
Glyptorthis as a rule is generally only slightly folded, but in Eridorthis the sul- 
cus is deep and the fold quite elevated. These features give the genus the ap- 
pearance of Oxoplecia or Cliftonia. In making Eridorthis, Foerste emphasized 
