214 NEW YORK STATE MUSEUM 



with margins truncated and meeting at right angles is evident. 

 In other respects we may note the following characters : The shell 

 is relatively suberect without posterior hinge, obliquely elongate, 

 suboval with greatest width across the pallial region, the hinge 

 line being short, not more than one half as long as the length 



Myalina p t e r i n a e oi d e s 



of the shell. The valves are shallow and thick; posterior muscle 

 scar well defined, situated at one half the length of the shell; 

 pallial line short, barely reaching beyond. the middle; anterior scar 

 absent. 



The surface of the shell is coarsely rugose in concentric growth 

 lines and is without other ornament. Of such a species as this 

 we Jmow nothing among the faunas of the Appalachian early 

 Devon ic. 



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



Cyrtodonta beyrichi Beushausen 



Cyrtodonta beyrichi Beushausen. Beitr. zur. Kenntn. d. Ob- 

 erharzen Spiriferensandsteins. 1884. p. 67, pi. 3, fig. 2, 3. 



I am disposed to refer to this species without much reservation 

 certain subcircular shells of Paracyclaslike outline with quite con- 

 vex surface, slightly depressed behind and faintly sinuous in front. 

 In these the hinge has the structure of Cyrtodonta strongly de- 

 veloped — the curved double anterior teeth and the long lateral 

 or posterior grooves and ridges. Beushausen's figures were made 

 from internal casts but they display the general outline and size 

 of those before us. 



The genus Cyrtodonta has not been observed in the Devonic 

 rocks of the Appalachian province and its occurrence in the eastern 



