CLASS II BRACHIOPODA 387 



ScaccJiinella Gemmellaro. Near to Derhya, but with excessively high 

 ventral cardinal areas. Ventral beak cemented ? Shells resemble EicMlio- 

 fenia, but have originated in some Orthotetinae and not in the Productinae, 

 Permian ; Sicily and Austria. 



Arctitreta Whitfield. Imperfectly known, but seemingly a member of the 

 Orthotetinae. Upper Carboniferous ; Arctic America. 



Streptorhynchus King. Very much like Schuchertella, Ventral area high, 

 short, twisted and probably cemented. Carboniferous and Permian ; America, 

 Europe and India. 



Meekella White and St. John. Very biconvex shells, with the teeth of the 

 ventral valve supported by very long dental plates which are nearly parallel 

 and reach to the bottom of the umbonal cavity ; no median sej^tum. Surface 

 of valves with coarse costae and fine, radiating, often plumose striae. Upper 

 Carboniferous ; North America, Eussia, India and China. Subgenus : Ortlio- 

 thetina Schellwien. Like Meekella, but without costae. Late Upper Carboni- 

 ferous and Permian ; Europe. 



Geyerella Schellwien. Near to Meekella, but with very high ventral areas ; 

 very long dental septa converging and uniting in a median septum. Ventral 

 beak cemented. Upper Carboniferous and Permian ; Europe. 



S^ibfamily E. Tripleciinae, novum. 

 Biconvex Strophomenids with marked fold and sinus. 



Triplecia Hall (Dicraniscus Hall). Trilobate, unequally biconvex, short- 

 hinged shells. Cardinal process long, erect and bifurcate. Surface smooth. 

 Ordovician and Silurian ; North America, England and Bohemia. 



Cliftonia Foerste. Striated Triplecia. Ordovician and Silurian of America 

 and Europe. 



Mimidus Barrande. Like Triplecia, but with the median fold on the 

 ventral valve. No external evidence of a deltidium. Silurian ; Bohemia and 

 North America. 



Streptis Davidson. Like Triplecia, but biconvex and bilaterally unsym- 

 metrical. Exterior with lamellar concentric shell expansions, Silurian ; 

 Europe and North America. 



Family 2. Thecidiidae Gray. 



Cemented Strophomenacea, in which the interior of the shell is impressed with 

 variously indented brachial furrows. Carboniferous to Recent. 



This family was formerly associated with the Terebratulidae. Beeclier has shown, 

 however, that brachial supports are wanting, and that a true deltidium is present. 



Subfamily A. Leptodinae, novum. 

 Thecidiidae with the brachial markings common to both valves. 



Keyserlingina Tscherny. An early form of Leptodus, with few brachial 

 ridges. Upper Carboniferous ; European Eussia and Austria. 



Leptodus Kayser (Lyttonia Waagen ; JFaagenopora Noetling). Very large, 

 highly inequivalved, irregular shells, frequently with broad lateral expansions. 



