NO. 2 BRACHIOPOD SUPERFAMILY STENOSCISMATACEA GRANT 



115 



beak moderately long for genus, somewhat attenuate on some speci- 

 mens, suberect to slightly incurved, apex sharply pointed ; beak ridges 

 rounded, indistinct ; delthyrium open, without deltidial plates ; foramen 

 not penetrating apex of beak. 



Brachial valve more strongly convex, greatest convexity near mid- 

 length ; beak obtusely pointed, apex within pedicle valve. 



Pedicle valve interior with dental plates converging on floor near 

 apex to form sessile spondylium, becoming elevated about 1-2 mm. 

 anterior, supported by low median septum duplex, extending ante- 

 riorly about one-fourth length of valve, septum extending slightly 

 farther. 



Brachial valve interior with short hinge plate in apex; crura ex- 

 tending anteriorly from forward edge of hinge plate, curving ventrally ; 

 camarophorium beginning against floor of valve immediately anterior 

 to apex, beginning as small swelling at top of median septum, con- 

 nected to base of hinge plate by low, short intercamarophorial plate, 

 continuing anteriorly about one-third length of valve, concave trans- 

 versely, strongly curved longitudinally toward end of spondylium of 

 opposite valve. 



Holotype.— McChesney (I860, 1868) plate 6, fig. 7 ( Plastoholotype 

 in Walker Museum, Univ. Chicago, No. 12424, illust. by Weller, 1914, 

 plate 23, figs. 46-47; duplicate in U.S. National Museum, No. 62495). 



Growth. — In this species both the width and the thickness are 

 slightly accelerated with respect to increase in length, in contrast 

 to the more common pattern where increase in width is isometric 



- a O<3 



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B 



D 



F G H 1 



Fig. 27. — Coledium explanation (McChesney), Chester Series, Chester, 111.; 

 sections by Weller (1914, p. 174, fig. 4, B-H, J-K), X3^. 



