1 82 NEW YORK STATE MUSEUM 



On the ventral valve the cardinal area is relatively high and sharply 

 defined while on the other this area is extremely narrow. In dimensions 

 these shells seldom exceed a width on the hinge of 20 mm and a length 

 of 12 mm. 



Localities. Everywhere along the coast at Grande Greve, Lehuquet's 

 and Indian Cove and one of the most abundant of all fossils in Perce Rock. 



Observations. The subgeneric term Metaplasia was introduced by 

 Hall & Clarke for spirifers with smooth lateral slopes, fold and sinus on 

 ventral and dorsal valves respectively and was applied to Hall's Spirifer 

 pyxidatus from the Oriskany of Cumberland, New Jersey, New York 

 and the Decewville beds of Ontario. There would be an obscuration of 

 the original purpose of this name in applying it to a species like S. p 1 i c a t a. 



Spirifer modestus Hall var. nitidulus no v. 



Plate 31, figures 18-24 



In the Helderbergian beds of Cumberland, Md. is a small Spirifer 

 described as S. modestus which expresses in its outward form and char- 

 acters the usual features of the Middle Devonic genus Ambocoelia save for 

 the greater convexity of the dorsal valve. Ambocoelia unquestionably 

 belongs in this category but has certain differentials in the arrangement of 

 the dorsal adductor scars and cardinal structure. In the Grand Greve lime- 

 stone we frequently find a diminutive shell, much smaller than S p. modes- 

 tus which carries similar characters. Its ventral valve is high and arched 

 at the umbo, its lateral slopes abrupt, the cardinal area high and gently 

 arched, with its sides but indistinctly defined and rounding out into the car- 

 dinal slopes of the valve, and the surface with a low median sinus but without 

 other markings. 



The dorsal valve is depressed convex, more elevated than in Ambo- 

 coelia, less so than in S p. modestus. On the interior the narrow del- 

 thyrium of the ventral valve is bounded by thin dental lamellae which do 

 not reach the bottom of the valve ; the dorsal valve has an extremely narrow 

 hinge area and prominent oblique crural bases. The muscle scars are not 

 discernible on either. 



Dimensions. The shells seldom attain a dimension greater than a 

 length and a width of 5 mm. 



Spirifer modestus Hall was first described in the loth Annual 

 Report of the New York State Cabinet of Natural History, 1857, page 61, 

 and subsequently redescribed with illustration in Palaeontology of New York, 

 1859, volume 3, page 203, pi. 28, fig. la-f. 



The variety nitidulus is also present at Glenerie, N. Y., where the 

 approach to Ambocoelia in the flatness of the dorsal valve is often more 

 pronounced. On comparison of shells from the two localities it appears 



