EARLY DEVON 1C HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 117 



more sharply angulated on the Maine specimens; in some of the German 

 specimens this angulation is apparent only in later growth. The fold is the 

 counterpart in these characters. 



5 Internal characters. Most notable independently and in point of 

 agreement are the very long dental plates, which diverge rather more in the 

 German than in the American form. In the Hartz specimens these plates 

 lie uniformly in the first radial grooves and hence diverge at the angle of 

 divergence of the radii. In the American shells they are quite as uniformly 

 subparallel to each other and thus are not parallel with the radii but transect 

 the proximal end of first sulcus and plication. This is a slight but persistent 

 difference. The muscle area in both shells is but faintly defined on the 

 ventral valve. 



Locality. Presque Isle stream. 



Spirifer cymindis Clarke 



Plate 30, figures 6-8, 10, i r 



Spirifer cymindis Clarke. N. Y. State Mus. Bui. Toy. 1907. p. 255 



This is a shell belonging to an extensive group of early Devonic species 

 which I presume are all minutely fimbriate (as in S. concinnus Hall) 

 though not in all have the surface characters been fully determined. Distinc- 

 tions are refined in this series of fossils and the differentials of the shells before 

 us can best be indicated by comparisons with other members of this series. 



In a general way, however, it may be said that S. cymindis is a 

 shell of larger size and stouter proportions than S. subcuspidatus 

 lateincisus. The form is short-winged with a prominent and arched 

 ventral beak, well developed subangular median sinus and fold, the width of 

 the former equaling the distance between three to four radial furrows ; of 

 the latter that of three plications. Both sinus and fold have abruptly slop- 

 ing sides and a narrow bottom and top. The primary plications are con- 

 spicuous by their elevation beyond the rest. The radial plications are 

 rounded on the exterior with sharp and narrow furrows, sharper on the inter- 

 nal cast with broader furrows. There are seven to eight plications on each 

 lateral slope. In rare instances there is a faint median plication in the sinus. 

 Fine concentric growth lines with traces of fimbriae cover the surface. 



The dental lamellae are short, divergent and inconspicuous, the muscle 

 scar of the ventral valve small, well defined, deeply divided by the median 

 sinus. The shell is not greatly thickened about this area and the inner 

 surface adjoining is rarely pustulose. 



Comparisons. S. concinnus Hall. In this Helderbergian and 

 Dalhousie form we have a shell of like proportions but with much more 

 elevated ventral beak and broader cardinal area, more abundant plication, 

 10 to 12, greater width of fold and sinus and extended projection of the 

 sinus on the anterior margin. 



