NO. 2 BRACHIOPOD SUPERFAMILY STENOSCISMATACEA GRANT 125 



umbo more or less tightly ; delthyrium trigonal, entirely rilled in adults 

 by brachial beak ; foramen small, slot-shaped, penetrating apex of beak. 



Brachial valve more strongly convex, umbonal region greatly swol- 

 len ; apex of beak curved into delthyrium of pedicle valve. 



Pedicle valve interior with dental plates uniting just above floor to 

 form large, boat-shaped spondylium, sessile or nearly so at apex, in- 

 creasingly elevated anteriorly on low median septum, extending an- 

 teriorly about one-third length of valve, about one-fourth length along 

 curvature of valve, septum extending slightly beyond anterior of 

 spondylium. 



Brachial valve interior with high cardinal process formed partly by 

 curved apex of valve beak ; hinge plate short, shallowly divided at 

 midline ; crura curving slightly ventrally from anterior edge of hinge 

 plate; camarophorium long, shallowly spoon-shaped, widening ante- 

 riorly, curving moderately strongly toward ventral valve, supported 

 by high but short median septum (camarophorium extending ante- 

 riorly about one-third length of valve ; septum extending along floor 

 about one-fifth length) ; intercamarophorial plate thick, extending 

 from trough of camarophorium to underside of hinge plate, projecting 

 nearly 1 mm. anterior to hinge plate. 



Holotype.— USNM 142448, plate 18, fig. 5a. 



Comparisons. — Coledium opimum is characterized by its rather 

 large size for the genus (the large ones could not be measured accu- 

 rately, so their measurements are not given below), strong convexity 

 with swollen beak regions, strongly curved pedicle beak, foramen that 

 penetrates the apex of the beak, and its weak or absent costae. In the 

 last feature it resembles C. erugatum n. sp., differing in its larger size, 

 more swollen pedicle beak, narrower outline, and in small juveniles, its 

 emarginate anterior. Its weak or absent costae, more swollen beak, 

 narrower outline and greater convexity distinguish it from C. torvum 

 n. sp. which also reaches nearly the same size. C. therum (Walcott) 

 attains a larger size than C. opimum, has stronger costae, not as thick- 

 ened nor strongly curved pedicle beak, and some specimens have a 

 short stolidium. Other species of the genus are easily distinguished 

 from C. opimum, normally by their smaller size, or stronger costae. 



Table 26. — Measurements of illustrated specimens of Coledium opimum from the 

 Pennsylvanian of Chariton County, Mo. 



Measurements, in millimeters 



USNM No. Length Width Thickness 



142446 c.6.5 5.7 3.6 



142447 c.8.4 7.0 4.4 



142448 10.0 c.10 8.4 



