NO. 2 BRACHIOPOD SUPERFAMILY STENOSCISMATACEA GRANT 41 



Pedicle valve flatly convex, slightly swollen just anterior to beak, 

 strongly curved through sulcus, flanks abruptly bent toward commis- 

 sure ; beak sharp, strongly curved to suberect or erect position ; beak 

 ridges short, distinct but not sharp ; posterolateral slopes slightly com- 

 pressed; delthyrium small, triangular, constricted by a pair of small 

 deltidial plates leaving small slit-shaped foramen. 



Brachial valve more strongly convex in adults, convexity normally 

 fairly even, slight swelling near beak in some individuals; margins 

 abruptly bent toward commissure, producing flat anterior ; beak short, 

 blunt, apex inside delthyrium. 



Pedicle valve interior with dental plates slightly convergent toward 

 floor near apex, meeting floor in extreme apex of some specimens, 

 normally bending abruptly just above floor to converge and fuse with 

 one another, forming elevated deep spondylium, continuing to floor 

 as median septum duplex supporting spondylium ; anterior edges of 

 dental plates concave anteriorly, extending along sides of spondylium 

 only about 1 mm. ; floor of spondylium extending anteriorly as shallow 

 trough for about 4 mm. ; median septum increasing in height only 

 slightly anteriorly, extending about 5 mm. anterior to pedicle beak, 

 slightly farther than spondylium ; muscle and pallial marks not ob- 

 served. 



Brachial valve interior with short median septum in apex, increas- 

 ing greatly in height toward anterior ; crest of septum spread to form 

 narrow, elongate, shallow camarophorium, beginning near floor of 

 valve in apex as slight swelling of crest of septum, becoming well-de- 

 fined trough less than 1 mm. anterior to beak ; median line of trough 

 intersected by low duplex intercamarophorial plate extending from 

 underside of hinge plate, extending forward beyond hinge, there form- 

 ing median septum in camarophorium with free crest; hinge plate 

 short, anteriorly tapering, apical part slightly swollen to form cardinal 

 process ; crura extending anteriorly from anterior edge of hinge plate, 

 long slender, curving ventrally, somewhat shorter than camarophorium 

 or ventral spondylium ; muscle and pallial marks not observed. 



Holotype.—USNM 141966, plate 1, fig. 7. 



Growth. — The graphic pattern of growth for this species is normal 

 for the genus, with points indicating the length-width ratio clustered 

 narrowly along a straight line, and those representing the length- 

 thickness ratio somewhat more widely spread along a curve of gentle 

 acceleration (fig. 6). Young shells are slightly elongate, and mature 

 shells somewhat transverse ; only one shell is as thick as it is long. 

 Projection of the length- width trend toward zero or 0.5 on the length- 

 axis indicates a slight change in slope, probably resulting from allo- 

 metric growth at the smallest post-larval stages. The length-thickness 

 curve can be projected with little or no change in curvature. 



