BRACHIOPODA — TELOTREMATA. 28 1 



TELOTREMATA. 



LXXIII. Orthorhynchula Hall and Clarke. 



Rostrate, with narrowed beaks. Hinge-line straight, extending 

 about one third the transverse diameter of the valves. Cardinal 

 area present on both valves, that of the pedicle valve being the 

 higher ; deithyrium open. No dental lamellae in the pedicle valve. 

 Cardinal process linear. Surface strongly plicate. It thus re- 

 sembles both Orthis and Rhynchonella. Ordovicic. 



239. 0. linneyi (James). (Fig. 342, d, e.) Ordovicic. 

 Median fold and sinus well developed. Average length f inch, 



width f inch, thickness i inch. 



Lorraine of Kentucky, Tennessee, Ohio. 



LXXIV. Rhynchotrema Hall. 



Rostrate, thick-shelled. Pedicle valve, with apex closely in- 

 curved over that of brachial. Teeth strong. Deltidial plates 

 concave, thick, cemented firmly to the bottom of the valve. 

 Brachial valve with a thickened median septum. Cardinal pro- 

 cess slender, linear, with broad and stout crural plate on each side. 

 Ordovicic and Devonic. 



240. R. inequivalve (Castelnau). (Fig. 343, a-d.) Ordovicic. 

 Small. Pedicle valve strongly convex at umbo and nearly flat 



on each side of the deep median sinus, sloping laterally. Brachial 

 valve more convex than the pedicle. Surface marked with prom- 

 inent subangular plications, 15-22 on each valve with 3-5 on the 

 fold and 2-5 in the sinus, crossed by very delicate concentric zig- 

 zag lines. 



Trenton. Widely distributed throughout North America. 



241. R. dentatum Hall. (Fig. 343, e-g.) Ordovicic. 

 Pyramidal with breadth somewhat greater than length. Beak 



of pedicle valve small and acute, closely incurved over that of the 

 brachial valve. Pedicle valve with a broad, deep and angular sinus, 

 strongly elevated toward the front. Surface marked by 8 or 9 

 strong and deep plications, two of which are very much elvated on 

 the fold of the brachial valve and one of which occupies the sinus 

 of the pedicle valve. 



Trenton and Lorraine of New York, Tennessee, Ohio, Indiana. 



