BRACHIOPODA. 215 



There is considerable variation in exterior among the Camarophorias. C. 

 Schlotheimi is a triangular or deltoidal shell with the plication clearly developed 

 on fold and sinus, but obscure on the lateral slopes. The greater number of 

 the European and Indian Carboniferous and Permian species have a similar 

 exterior. In C. Schlotheimi, von Buch, and C. Humbletonensis, Howse, the margins 

 of the shell are, normally, expanded as in some Devonian forms of Airypa reti- 

 cularis. Camarophoria subtrigona, Meek and Worthen, C. isorhyncha, McCoy, are 

 large subcuboidal species, while C. ringens, Swallow, C. caput-testudinis, White, 

 and C. subcuneata. Hall, are acutely triangular in outline, with broad, concave 

 cardinal slopes. The species of both the latter groups are strongly plicated 

 throughout, while in C. ringens the surface also bears a fine radiate linea- 

 tion. 



The Camarophoria (Pentamerus) lenticularis, White and Whitfield, from the 

 Yellow sandstones beneath the Burlington limestone, at Burlington, Iowa, is a 

 shell widely different from all the foregoing in external features. The valves 

 are biconvex and their outline subcircular ; it has no fold and sinus and no 

 plications, the surface being smooth and regularly arched. To associate it 

 generically with the plicate trihedral Camarophorias requires an effort of the 

 imagination. At the same time its internal characters are normal for Camaro- 

 phoria, except that the broad, spatuliform spondylium rests upon the valve 

 for most of its length, the median septum penetrating it and projecting 

 above it into the interior cavity of the shell. It is proposed to signalize 

 these differences, and thus to render the association constituting Camaro- 

 phoria the more homogeneous, by giving this species the subgeneric designa- 

 tion, Camarophorella. 



