EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA II9 



3 Surface. The median sinus has a width of from two to two and one 

 half lateral furrows, its sides being highly divergent, sloping abruptly to the 

 bottom which is sometimes quite sharp. The primary plications are con- 

 spicuous and elevated. On the sides there are four, rarely five, plications, 

 in extreme cases greatly subordinated to the median ones and separated by 

 broad furrows. The sculpture of the surface consists of rather coarse and 

 moderately distant concentric lines which may become lamellose. 



4 Interior. The dental plates are as in S . c y m i n d i s. The muscle 

 scar of the ventral valve is deeply impressed and sharply defined, specially 

 in old shells where the test is thickened in the umbonal region. The 

 removal of this thickened shell leaves internal casts with a prominent 

 muscle area, the surfaces adjoining which are pustulose. There is no 

 median septum in this valve. In young shells the ribs are sharp on the 

 internal cast but are rounder on old shells. 



The features here summarized constitute an expression not represented 

 in the Appalachian faunas and so far as we can ascertain not exactly 

 reproduced in the Coblentzian. 



Locality. Edmunds Hill. 



Spirifer aroostookensis Clarke 



Plate 30, figures 5, 9 ; pi. 34, figures 6-16 

 Set r. 1.(3 



Spirifer aroostookensis Clarke. N. Y. State Mus. Bui. 107. 1907. p. 258 



This shell is characterized by its broad, fiat ribs with very narrow- 

 radial furrows, in which respect it is remarkably similar to S. mesastri, 

 alis Hall of the Upper Devonic (Ithaca group) of New York. Of these 

 lateral ribs there are 10 to 12 on each side and each of the laree ones bears 

 a slight furrow along its flat top. The median fold is relatively narrow and 

 not highly elevated. The shell is short-hinged and rotund in form. The 

 surface is covered with close concentric fimbriate lines which bend back- 

 ward at the middle of each sulcated rib. I have seen but a single dorsal 

 valve of this interesting species but its differential characters are very 

 distinct. As noted on page 143 of this volume, this species has proven to 

 be common in recently discovered outcrops of the Oriskany in New York. 



Locality. Edmunds Hill. 



Spirifer macropleuroides Clarke 



Plate 30, figures 3, 4 



Spirifer macropleuroides Clarke. N. Y. State Mus. Bui. 107. 1907. 1x259 



The Chapman Plantation fauna carries a representative of the Radiati 

 or group of Spirifer plicatellus in a species which has the aspect 



