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NEW YORK STATE MUSEUM 



or pitted. In the dorsal valve there is a large perforated hinge 

 plate, the foramen apparently always open in contrast to the con- 

 dition of old specimens of A. e 1 o n g a t a. The external surface 

 is marked by rather strong concentric lines with some radial lines 

 along the middle of the valves. 



Lower Devonic. Moose river at Stony brook and Moosehead 

 lake, Baker Brook point, Me. 



Beachia amplexa no v. 



B. suessana and Megalanteris ovalis Hall are two 

 very similar brachiopods in the Oriskany fauna. Whenever a con- 

 siderable number of specimens of both are available, those of the 

 latter are, as Professor Hall noted in 1859, generally larger, more 

 compressed and proportionally broader. Further differentials are 

 found in the more broadly rounded anterior margin of the latter, 

 the absence of introverted margins except at the cardinal shoulders 

 and a low radial surface striation, coarser but more obscure than in 

 Beachia, and restricted to the marginal regions rather than cover- 

 ing the entire shell as in that genus. The critical distinction in 



■ . Beachia amplexa 



the genera however is an internal one based on the structure of 

 the cardinal process. These features have been elaborately illus- 

 trated by Hall and Clarke^ whose figures show that in B. sues- 

 sana this process is distinctly rensselaeroid and consists of two 

 flattened subtriangular plates fused medially and thickened or 

 cushion-shaped at the sides with a median foramen beneath the 

 beak which is closed only by excessive calcification. In M. o v a 1 i s 

 this cardinal process is stout, subcylindrical, doubly grooved at the 

 extremity and rising from a flat hinge plate, as though in effect 

 the single cylindrical process were superinduced on the hinge plate 

 of a Beachia. 



iPal. N. Y. 1894. V. 8, pt 2, pi. 77. 



