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NEW YORK STATE MUSEUM 



defined radial ridges ; the umbonal ridge, separated from the me- 

 dian ridge by a moderately deep broadening groove and in front 

 of this a depression bounded by a still lower sometimes quite vague 

 elevation. Some of Beushausen's species of Prosocoelus, espe- 

 cially P. ellipticus (Schalke, Hartz) have much the outline 

 and expression of this shell. There are specimens in our collec- 

 tions that indicate a more orbicular outline quite similar to that 

 of P. orbicularis Beushausen.^ I am not altogether certain 

 whether these represent the latter species or may be compressed 

 specimens of the former. The evidence seems to favor the former 

 view. 



Lozver Devonic. Tomhegan point, Moosehead lake. Me. 



Leptodomus communis nov. 



Shell elongate with a Cimitarialike curve to the hinge, beak 

 anterior, hinge not equaling the length of the shell ; lower margin 

 sinuate, curving upward posteriorly to a narrowed, subacute ex- 



Leptodomus communis 



tremity whence the posterior edge retreats to the hinge. Surface 

 deeply sulcate from umbo to basal margin. Umbonal ridge con- 

 spicuous, blunt and broadly curved, exterior with low irregular 

 concentric folds. 



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



Leptodomus corrugatus nov. 



Shell small, beak at the anterior third of the hinge, outline sub- 

 elliptical, posterior slope gently sulcate, smooth, anterior surface 



Leptodomus corrugatu! 



coarsely corrugated and over the median area these anterior ridges 

 duplicate, there being on the whole on the lateral slope two 



Hhid. p. no, pi. 5, fig. 8. 



