SOME NEW DEVONIC FOSSILS 25 1 



The internal markings are essentially as in the other species, the 

 ventral adductor scar being even more conspicuous, the cardinal 

 plate less developed. 



Lower Devonic. Grande Greve and Perce rock, P. Q. 



Meristella champlaini ncv. 



Specimens of Meristella are among the commonest fossils in the 

 Grande Greve limestones. Adult forms of this species share with 

 immature individuals a well defined habit which can be readily 

 distinguished from the known characters of one and another of 

 the many species of the genus which have already been described 

 from the faunas of about this age. 



Into immediate comparison with these shells we bring the fol- 

 lowing known forms : M. 1 a e v i s, M. arcuata, M. s u b - 



Meristella champlaini 



quadrata of the Helderbergian fauna ; M. lata and M. v a s - 

 c u 1 a r i a of the Oriskany fauna. Comparisons therewith are in- 

 troduced seriatim. 



Meristella laevis Vanuxem (A trypa laevis Vanux, 

 Geol. N. Y. : Rep't on Third Dist. 1842. p. 120, fig. 2; 

 Merista laevis Hall, Pal. N. Y. 1859. 3 1247, pi. 39, fig. 

 3, 4; Meristella laevis Hall & Clarke, Pal. N. Y. 1894. 

 v. 8, pt 2, pi. 43, fig. 3-6) is a rather elongate shell with long 

 cardinal slopes making a relatively small angle with each other. 

 Both valves are moderately and subequally convex, the ventral 

 valve faintly sinuate medially in old stages with a broad and rather 

 short linguate extension on the front margin, which when slightly 

 broken, as in most of Hall's figures, gives the front a subtruncate 

 appearance. The dorsal valve has a broadly defined median ridge 

 in all stages, but obscure near the margin in the adult. On the 

 interior there is seldom any trace of vascular impressions depart- 

 ing from the muscular area. 



