Upper Helderberg Group. 439 



striae ; external striae fine, distinct. At irregular intervals are rows 

 of spines having a diameter at the base of 1 m. and a length of from 

 2 to 3 mm., about 4 in the space of 5 mm.; number of lamellae 90, 

 alternating in size. This species may be distinguished by its promi- 

 nent, irregular, annulations and the concentric rows of spines. 



Formation and locality, Corniferous limestone, Oharlestown, 

 Indiana. 



Zaphrentis concava, n. sp, 



Corallum simple, turbinate, regularly curved; height 25 mm.; diam- 

 eter of the calix 20 mm., depth 10 mm., the sides of the calix quite 

 abruptly descending to within 4 mm. of the center, where there is a 

 narrow elevation surrounding an abrupt concavity of 5 mm. in diam- 

 eter; fossette narrow, deep, indenting the margin of the concave 

 space and extending to the anterior margin of the calix ; number of 

 lamellae 70, alternating in size, a few extending to the center ; tabulae 

 concave in the center, outer portion bending abruptly downward, 

 intermediate portion convex. 



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



Zaphrentis Herzeri, n. sp.TlJt.F,'* j&l** 



Corallum simple, turbinate, straight or curved; frequently, and 

 especially in young individuals, the anterior side is flattened ; base 

 acute, quite regularly expanding to the calix ; exterior with numerous 

 rounded annulations and concentric striae; external striae, in all 

 the individuals observed obscure ; sometimes attaining a height of 40 

 mm., but usually 30 mm.; diameter of the calix from 15 to 20 mm., 

 depth from 10 to 15 mm., more or less oval, usually flattened near the 

 margin, then abruptly sloping to the center ; fossette narrow, extend- 

 ing from the center nearly to the anterior margin ; number of lamellae 

 from 60 to 70, alternating in size, the smaller ones not more than 5 

 mm. in length, the others extending to the center of the cup, not 

 twisted or elevated. This species has been included with Heliophyllum 

 exiguum by Dr. C. Rominger, Geological Survey of Michigan, but the 

 form is entirely different and there are no traces of heliophylloid struc- 

 ture ; from Z. ungula it may be distinguished by its less compressed 

 form, and the entirely different character of the center of the calix. 



Formation and locality. Corniferous limestone, Louisville, Ken- 

 tucky. 



Zaphrentis curvata, n. sp a 

 Corallum simple, turbinate, curved, base acute, regularly ex-- 

 panding to the calix ; exterior with numerous sharp annulations of 

 growth and concentric striae; external striae distinct, 12 in the 



