2l6 NEW YORK STATE MUSEUM 



Megambonia denysia nov. 



Shell very small, suborbicular in outline and rotund in contour. 

 Auricle not prominent, byssal groove broad shallow and indistinct, 

 but visible nearly to the beak. Surface very finely radiate on 

 the body of the shell but with fewer radii on the auricle. The 



Megambonia denysi 



orbicular outline, regular convexity and feeble byssal groove seem 

 to indicate this as distinct from M. crenistriata Clarke, 

 though not varying materially in surface characters. Further knowl- 

 edge of the shell may determine a closer relationship in the two. 

 Lower Devonic. Perce rock, P. Q. 



Mytilarca dalhousie nov. 



Ct. M. o v a t a Hall. Palaeontology of New York, 3: 279, pi. 50, fig. 7. 

 M. solid a Maurer. Fauna d. rechtsrhein. Unterdevon. 1886. 

 p. 13; Freeh. Devon. Aviculiden Deutschlands, p. 143, fig. 15. 



Mytilarca is not common in early Devonic faunas. The speci- 

 mens of the genus from the Dalhousie fauna are well developed 

 in respect to generic characters and of moderately large size 

 approaching in dimensions the Helderbergian species Megam- 

 bonia ovata Hall which has never been well described or 

 figured though its relation to Mytilarca has long been recognized 1 ; 

 and in outline and contour Myalina solida Maurer of the 

 Lower Coblentzian where such species are rare. Mytilarca 

 dalhousie is elongate subovate in outline, with short straight 

 posterior hinge and long abruptly deflected anterior margin extend- 

 ing to the basal curvature of the valves with a slightly sinuous 

 curve. The surface is regularly but slightly convex with the 



*N. Y. State Mus. Mem. 3, p. 89. 



