258 NEW YORK STATE MUSEUM 



lateral margins rather directly convergent. The ventral valve is 

 elevated at the beak, the cardinal area being rather high and curved, 

 and the median part of the shell elevated. 



3 Surface. The median sinus has a width of from two to two 

 and five tenths lateral furrows, its sides being highly divergent, slop- 

 ing abruptly to the bottom whch is sometimes quite sharp. The pri- 

 mary plications are conspicuous and elevated. On the sides there 

 are four, rarely five, plications, in extreme cases greatly subordi- 

 nated to the median ones and separated by broad furrows. The 

 sculpture of the surface consists of rather coarse and moderately 

 distant concentric lines which may become lamellose. 



4 Interior. The dental plates are as in S. cymindis. The 

 muscle scar of the ventral valve is deeply impressed and sharply 

 defined, specially in old shells where the test is thickened in the 

 umbonal region. The removal of this thickened shell leaves in- 

 ternal casts with a prominent muscle area, the surfaces adjoining 

 which are pustulose. There is no median septum in this valve. In 

 young shells the ribs are sharp on the internal cast but are rounder 

 on old shells. 



The features here summarized constitute an expression not rep- 

 resented in the Appalachian faunas and so far as we can ascertain 

 not exactly reproduced in the Coblentzian. 



Lower Devonic. Presque Isle stream. Chapman Plantation, Me. 



S|)irifer aroostookensis nov. 



This shell is characterized by its broad, flat ribs with very nar- 

 row, radial furrows, in which respect it is remarkably similar to 



Spirifer aroostookensis 



S. mesastrialis Hall of the Upper Devonic (Ithaca group) 

 of New York. Of these lateral ribs there are 10 to 12 on each 



