3:26 MOLLUSCOIDEA BRACHIOPODA SUB-KINGDOM v 



(SECTION A.) TEREBRATULA.. 



Terebi-atulacea with the loops unsupported by a median doi'sal septum at any stage 

 of growth. Brachial cirri directed outwards in larval stages. 



Family 1. Centronellidae. Hall and Clarke. 



Terebratulas with the loops developing direct and composed of two descending 

 lamellae, uniting in the median line and forming a broad arched plate. Devonian 

 to Triassic. 



This family comprises the simplest of all Terebratuloids, and from it are probably 

 descended the other loop-bearing families. 



Centronella, Billings (Fig. 547). Commonly small, smooth, plano-convex, 

 or concavo-convex shells, with the descending branches of the loop broadening 

 rapidly anteriorly, and uniting in a triangular, mesially ridged plate. 

 Devonian ; North America. 



Bensselaeria, Hall. Ovate or elongate-ovate striate Terebratuloids. The 

 descending branches of the loop diverging for a short distance, thence acutely 

 bent, converging, and uniting in an elongate triangular plate, which on the 



posterior margin gives off a small, pos- 

 teriorly directed, rod-like process. Hinge- 

 plate large and often much thickened. 

 Thick dental plates present. Lower 

 Devonian ; North America and Germany. 

 Beachia, Hall and Clarke. Lentiform 

 finely striated Eensselaeriae with the 

 lateral margins of the valves inflected, 

 the anterior plate of the brachidium 



Centronella glans-fa^H^l. Devonian ; Erie broader, and the rod-like prOCCSS longer. 



County, N.Y. A, B, Profile and dorsal aspect, 1/1- Lower Devonian ; North America. 



Newberria, Hall (fiensselandia, Hall). 



Resembling Piensselaeria externally, but without the striate surface. Interior 

 strongly marked by muscular scars and vascular sinuses. Devonian ; North 

 America and Europe. 



Oriskania, Hall and Clarke. Large Centronellae with a continuous hinge- 

 plate bearing a thin vertical spur or cardinal process. Lower Devonian ; 

 North America. 



Selenella, Hall and Clarke. Biconvex Terebratuliform shells with a 

 Centronella-like loop, but the triangular plate not mesially thickened. De- 

 vonian ; North America. 



Eomingerina, Hall and Clarke. Small biconvex Centronellae with the 

 median ridge on the anterior plate of the loop elevated into a high vertical 

 lamella almost touching the ventral valve and extended both anteriorly 

 and posteriorly. Devonian to Lower Carboniferous ; North America. 



Trigeria (Bayle), Hall and Clarke. Plicated, plano-convex Centronellae. 

 Devonian ; France, Brazil, and North America. 



? Scaphiocoelia, Whitfield. Very large, plicate, piano- or concavo-convex, 

 Centronella-like, shells exteriorly. Loop unknown. Shell substance fibrous, 

 impunctate. (?) Devonian ; South America. 



