Weller — Kinderhook Faunal Studies. 77 



covered with bifurcating plications. In this respect it is 

 allied to 8. grimesi H., of the Osage fauna, and may possibly 

 be considered as a genetic predecessor of that species. It 

 never grows so large as 8. grimesi, however, and has a shorter 

 hinge-line. It is not known whether the shell is marked by 

 the very fine radiating striae which characterize 8. grimesi. 



Spirifer biplicatus Hall. 



Pl.II.f. 6-7. 



Shell, exclusive of the cardinal extensions, semicircular or 

 semielliptical in outline; the hinge-line greatly extended in 

 long mucronate points. Pedicle valve with a rather small in- 

 curved beak and a prominent umbo ; the cardinal area narrow ; 

 the slope to the cardinal margin rather steep, that to the 

 cardinal angles and lateral margins slightly concave ; the 

 mesial sinus narrow and shallow, marked in the center by a 

 single, simple plication, the two bounding plications larger 

 than any of those on the lateral slopes. Convexity of the 

 brachial valve about equal to that of the pedicle valve, the 

 mesial fold narrow, not elevated above the general surface of 

 the valve, marked along its median line by a simple, shallow 

 furrow, the bounding furrows deeper than those on the lateral 

 slopes. Surface of each valve marked by about twelve simple 

 plications on each lateral slope which grow smaller as they 

 approach the cardinal angles, and by concentric lines of 

 growth. The dimensions of an average specimen are: length, 

 9 mm., breadth along the hinge-line, 50 mm., thickness, 

 8 mm. 



Remarks. This species is remarkable because of its greatly 

 extended, mucronate cardinal extremities. In this respect it 

 strongly simulates some Devonian species such as 8. pennatus 

 Atw., and has no near allies in the succeeding Carboniferous 

 faunas. We have then, associated in this fauna, this strictly 

 Devonian type of the genus Spirifer, and a characteristic 

 Carboniferous type represented by 8. subrolundatus. 



Syringothyris extenuatus (Hall). 



PI. I.f. 1-3. 



Shell subsemielliptical in outline, greatly extended along 

 the hinge-line. Pedicle valve subpyramidal ; the cardinal 



