252 



BEACHIOPODA. 



ElIYNCHONELLA MaUDENSIS. (N. Sp. ) 

 Plate 33, figs. 8, 8a and 8b. 



Shell small, modevately convex, the maximum thickness through 

 the closed valves being usually about one-third less than their greatest 

 breadth : length and breadth nearly equal in most specimens but in 

 others the breadth slightly exceeds the length ; outline varying 

 from rounded subtrigonal or broadly and longitudinally subovate to 

 subpentagonal and somewhat transversely elongated : front margin 

 more or less truncated or shallowly emarginated. 



Ventral valve tumid in the centre above, and contracting rather 

 suddenly into a broad and not very deep mesial sinus below : beak of the 

 same valve small and pointed, curved inward over that of the dorsal : 

 area small and narrow. Dorsal valve also gibbous and tumid in the 

 umbonal region above, convexly, obliquely and abruptly inflected on 

 both sides of the mesial fold below. 



Surface marked with sharply angular, or subangular radiating simple 

 ribs, which extend from the beaks to the anterior and lateral margins. 

 On the ventral valve there are from four to six ribs on the sinus, and 

 seven or eight on each side, while on the dorsal there are from five to 

 seven on the fold, and seven or eight on each side. 



Dimensions of a perfect specimen of average size : length eleven 

 millimetres : breadth, eleven : maximum thickness, seven mm. Some 

 individuals are not quite one mm. broader than long, and in others the 

 thickness is equal to nearly one-half the maximum breadth. 



South side of Maud Island, abundant and in good condition. 



An interesting little shell, which may prove to be only a small local 

 variety of the B. gnathophora of Meek. * 



DiSCINA SEMIPOLITA. (N. Sp.) 

 Plate 33, figs. 9 and 9a. 



Shell, (or rather upper valve, for the under or attached valye is un- 

 known) depressed conical : height from ajDCx to base about one-half or 

 a little less than one half the greatest breadth of the base : outline of 



* Palaeontology of California, Vol. 1, p,39. pi. 8, figs. 1 and 1 a—f. 



