Upper Helderberg Group. 427 



AULACOPHYLLUM PRATERIFORME, 71. §$. £l V},Tiu l?J . 



Carallum simple, turbinate, curved ; exterior with concentric 

 wrinkles and striations, and occasional constrictions ; height of cor- 

 alluui 30 mm., length of anterior side 50 mm., of posterior side 35 

 mm.; diameter of the calix 45 mm., depth 20 mm., quite regularly 

 concave, bottom of the calix a little posterior to the center ; fossette 

 narrow extending from the center to the anterior margin ; number of 

 lamellae 110, alternating in size, about 16 of the larger lamellae converge 

 to the fossette, the remainder continue to the bottom of the calix, 

 where they are slightly twisted, not elevated. In general appearance 

 this species is similar to A. convergens, but the anterior and posterior 

 sides are more nearly equal in length, the deepest part of the calix is 

 nearly central, while in that species it is posterior ; the converging of 

 the lamellae to the fossette is much less distinct. 



Formation and locality. Corniferous limestone, Falls of the Ohio. 



AULACOPHYLLUM PIN^ATUM, n. Sp.-t/zf<F/0f.*:/O, 



Corallum simple, turbinate, exterior with undulations of growth ; 

 longitudinal striations distinct; height 35 mm.; diameter of calix 30 

 mm., depth 25 mm., sides regularly sloping ; a narrow deep fossette 

 extends from the bottom to the anterior margin ; number of lamellae 

 from 80 to 90, alternating in size, the larger ones only reaching the 

 fossette and the bottom of the cup, near the margin, thickened, sub- 

 angular, becoming thinner on the sides ; convergence of the lamellae 

 to the fossette very distinct ; there are two rudimentary lateral fos- 

 settes and a less conspicuous one on posterior side. 



Formation and locality. Corniferous limestone, Falls of the Ohio. 



AULACOPHYLLUM PRINCEPS, 71. Sp.^J ^7,Pf6 />J-< 



Corallum simple, turbinate, regularly curved : exterior with numer- 

 ous irregular undulations of growth, concentric wrinkles and striations; 

 longitudinal striae, fine and very distinct ; height of adult individuals 

 from 70 to 100 mm.; diameter of calix from 40 to 50 mm., depth 30 

 mm. ; calix sometimes oval or subquadrangular, sides abruptly de- 

 scending, leaving a broad flat, or elevated space, at the bottom ; fossette 

 commencing anteriorly to the center, not continuing to the margin ; 

 number of lamellae from 160 to 180, at the margin of nearly uniform 

 size, on the sides the alternate lamellae are much larger than the 

 others ; about two- thirds of the lamellae converge to the fossette or to 

 a line in continuation of it, the remainder toward the center of the 

 calix ; near the center the lamellae are thickened and twisted. From 

 A. sulcatum it is easily distinguished by the greater number of and 

 thinner lamellae. 



Formation and localities, Corniferous limestone, New York and 

 Falls of the Ohio. 



