144 LOWER PENINSULA. 



STREPTELASMA CONULUS, N. Sp. 



Straight, conical, small-sized polyparia ; the larger ones attain a 

 diameter of one centimeter by one and a half in length ; surface 

 faintly annulated by lines of growth, not ribbed longitudinally as 

 in the similar form Streptelasma calycula. Calyces deep, with erect 

 margins surrounded by from twenty to twenty-five denticulated 

 lamellar crests of larger size, and by as many intermediate rudi- 

 mentary ones with likewise dentate edges ; the sides of the lamellae 

 are ornamented with transverse rugae. The larger lamellae unite 

 in the centre, as in the former species, into a horseshoe-formed 

 cycle which incloses a narrow core of lacunose, irregularly anasto- 

 mosing cell spaces ; the aperture of the horseshoe corresponds 

 with the principal septal fovea. 



Found associated with the former in the Niagara group of Drum- 

 mond's Island, etc. 



Plate XXXIX. — Fig. 4 represents a number of silicified specimens 

 from the above-named locality. 



STREPTELASMA SPONGAXIS, N. Sp. 



POLYDILASMA, Hall. 



Small, conical, horn-shaped polyparia, about two centimeters 

 wide by three in length in middle-sized specimens. Calyces mod- 

 erately deep, with slanting sides and slightly expanding margins, 

 surrounded by about thirty stout crests alternating with as many 

 intermediate smaller ones. Surface of lamellae decorated with gran- 

 ules and transverse rugae. -The lamellae unite in the centre into a 

 spongiose axal core, resembling the tissue of a macerated porous 

 bone. Septal fovea obscure. The apices of the cells exhibit 

 generally a strong sublateral scar of attachment. 



Found associated with the other forms in the Niagara group of 

 Drummond's Island, and at Point Detour ; also found at Mason- 

 ville, Iowa. 



Plate XXXIX., Fig. 2. — All the smaller specimens represent the 

 usual form as it occurs at Point Detour. The larger specimen is 

 from the Niagara group of Paul's Station, Indiana ; it does not 



