SOME NEW DEVONIC FOSSILS 243 



toR. crassicosta Koch of the Siegen greywacke is undeniable. 

 Lower Devonic. Misery stream, first dam in town of Sand- 

 wich, Me. 



Rensselaeria cf. crassicosta Koch 



See Koch. Neues Jahrb. fur Mineral. 1881. p. 237, and other German 

 authors 



There are a few shells of small size in a quartzite at the above 

 cited locality which are coarse ribbed and hardly to be distinguished 



Rensselaeria cf. crassicosta 



from specimens of R. crassicosta which I have received 

 from Professor Kayser. The dorsal valves show a long and much 

 thickened septum with a divided hinge plate. 



R. crassicosta is from the Taunas quartzite and Siegen 

 beds of the Coblentzian. 



Lower Devonic. Misery stream, first dam in town of Sand- 

 wich, Me. 



Rensselaeria atlantica nov. 



Rensselaeria mainensis Williams, U. S. Geol. Sur. Bui. 165. 

 1900. p. 80, not described or figured. 



The Rensselaerias of the Chapman Plantation faunas are of 

 singular interest for the type of structure they present. They 

 occur both in the Presque Isle stream outcrops and at Edmunds 

 Hill but there is a difference in the forms from the two localities 

 which is expressible in terms of development only. 



The Chapman Plantation shells have a naviculoid contour, that 

 is, the ventral valve is highly arched and elevated medially, the 

 beak conspicuous and overarching the hinge, the lateral slopes of this 



