Upper Helderberg Group. 425 



Streptelasma mammiferum, n. sp. ' (.*&•?/}/*■>/ J 



Corallum simple, turbinate, attenuate below, expanded on anterior 

 side, flattened on posterior side ; exterior with annulations and gentle 

 undulations ; longitudinal stria?, coarse, distinct; height 60 mm.; 

 calix oval, length 45 mm., width 30, sides abruptly sloping, a conical 

 elevation at the bottom 10 mm. iu height ; number of lamellae 70, 

 alternating in size (in some individuals this feature is much more 

 prominent than in others), near the margin broad, rounded, becoming 

 very thin as they approach the center, where they are twisted and 

 coalescing, forming a prominent false columella, with prolonged tip. 

 In some individuals where the internal structure can be seen there 

 are no evidences of tabulae, in others it would seem impossible that 

 the prominent elevations are formed by the lamellae alone, probably 

 in the larger specimens tabulae do exist. 



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



Streptelasma papxllatum, n. sp. A.Z#< F** /jf*/f* 



Corallum simple, turbinate, curved; exterior with gentle undula- 

 tions and a few sharp annulations ; height of corallum 50 mm.; diam- 

 eter of calix 35 mm., depth 25 mm., sides abruptly descending, leaving 

 a flat or concave space at the bottom of the calix, 15 mm. in diameter, 

 in the center of which is a conical elevation 5 mm. in height ; number 

 of lamellae 80, at the margin of nearly uniform size, alternating below, 

 the principal lamellae extending to the center, twisted and elevated, 

 forming a very much contorted false columella. 



This species most closely resembled S. mammiferum, but is more 

 abruptly expanding ; the calix is circular, not oblique ; the lamellae 

 are smaller, there are 8 or 9 in the space occupied by 6 in that species ; 

 the elevation on the bottom of the calix is not so prominent and is 

 of a somewhat different character. 



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



Streptelasma cpa.rctatum, n. sp. Pf*-*- P/* /&*/}, 

 Corallum simple, turbinate, curved, usually slightly compressed; 

 exterior with broad undulations; height 50 mm.; calix slightly oval, 

 greatest diameter 25 mm., depth 20 mm., sides regularly sloping to 

 the center, an elevation at the bottom 5 mm. in height ; fossette 

 obscure or wanting ; number of lamella 80, near the margin of uni- 

 form size, thickened and rounded, on the sides alternating, becoming 

 thin as they approach the center, the principal ones continuing to the 

 center twisting and coalescing. The elevation at the center might.be 

 considered as due to tabulae but there is no evidence of their existence 

 in the specimens examined. 



Formation and locality. Oorniferous limestone, Louisville, Ky. 

 [Sen. Doc. No. 38.] 54 



