Desoiptions of Neiv Species of Brachiopoda. 333 



wholly different from the Amhoni/chia, can never be affected by it or 

 any subgenus under it. So far, then, as anything is yet known the 

 genus Anomalodonta will hold its place in the zoological column, rep- 

 resented by at. least two species, Anomalodonta gigantm, the type, and 

 Anomalodonta alata. 



Deseriptiom of New Species of Brachiopoda, from the Lower Silurian 

 Formation, Cincinnati Group. — By U. P. James. 



Strophomena gibbom — James, 



S. gibbosa— J. MiBS. Catalogue of Lower Silurian Fossils, Sept. 1871. 



Shell fragile, semi-oval ; cardinal line extended to or a little beyond 

 the Avidth of the shell farther forward, deflected at the extremities ; 

 lateral and front margins regularly rounded. Ventral valve slightly 

 convex in the umbonal region, but at about one third or one half the 

 distance from the beak, toward the front and lateral margins, it curves 

 suddenly upward, then rounds off, and is deflected as suddenly the 

 other way to the front and sides, forming a high rounded ridge, giving 

 to the shell a decidedly gibbous form ; this hump extends to about ^th 

 of an inch of the cardinal line on each side, where the shell is rather de- 

 pressed from the umbonal slopes outw^ard to the deflected extremities 

 immediately in front of the cardinal line ; cardinal area linear ; beak 

 rather prominent, projecting, minutely perforated ; six to eight slight 

 wrinkles on the umbonal region. Surface covered by fine radiating 

 striaj, increased by interstitial additions, somewhat variable in size on 

 the front slope, but quite uniform on the unibone and to the lateral 

 margins; crossed by fine concentric stria. Interior not observed. 



Dorsal valve (exterior) gently concave to about the middle, Avhere it 

 makes a sudden curve, conforming to the shape of the other valve ; 

 the two valves are so closely drawn together as to leave scarcely any 

 visceral space ; beak very little elevated above the cardinal line ; area 

 no more than a rather sharp edge of the hinge ; radiating strite, as far 

 as observed, same as on the ventral valve. Interior nearly flat, or 

 slightly convex, to the base of the ridge in front, and laterally to 

 within about one quarter or one eighth of an inch of the cardinal line, 

 where there is a flat depression extending to the lateral margins ; the 

 curve to the front from the top of the ridge is abrupt, corresponding 

 to the exterior; cardinal process bifid, erect, rather prominent, curving 

 slightly anteriorly, crenulated posteriorly, and sloping in the same di- 



