OSTEACODA. 665 



Dioranella bicornis.] 



the question, are they really congeneric with the typical species?, depends, I should 

 say, entirely upon the significance we attach to the presence or absence of the 

 marginal frill. Believing that further investigations are desirable, I shall not 

 attempt to decide the question now. In the meantime the new species may be 

 known as a doubtful Dicranella, while the others had best remain where Prof. Jones 

 has placed them. ' 



Dicranella bicornis, n. sp. 



PLATE XLIV, FIG, 26. PLATE XLVI, FIGS. 39-40. 



Size. — Without border, length 1.5 mm.; bight 0.83 mm.; thickness 0.4 mm. 

 . With border, length 1.8 mm.: hight 1 .02 mm. 



Valves oblong, straight dorsally, rounded veritrally and at the ends, the latter 

 nearly equal. Two large, subequal, diverging, horn-like processes, angular in cross- 

 section, arise behind the center of the dorsal half and project far beyond the dorsal 

 edge; between their bases a suboval depression; lower half of. posterior horn with a 

 large rounded swelling. Outline of valves marked by a sharply defined, linear ridge; 

 beyond this a wide but very thin, smooth border or frill, usually bending outward 

 at the edge; border narrowest anteriorly, widest below. 



This species is so easily recognized by its "horns," that comparisons are quite 

 unnecessary. 



Formation and locality. — Lower and middle thirds of the Trenton shales (Stictoporella and Rhini- 

 dictya,beds), Minneapolis and St. Paul, Minnesota. 



Dicranella spinosa, n. sp. 



PLATE XLIV, FIG. 23. PLATE XLVL FIG. 41. 



Size.— Length (including border) 1.5 mm.; hight 0.8 mm.; thickness 0.45 mm. 



This species is similar to Z), bicornis but the valves are a little longer, and the 

 "horns" begin lower down on the valves and are not carinated, while the posterior 

 one is shorter, and seems not to extend beyond the rounded swelling. The border 

 also seems not to have been developed anteriorly, while along the ventral edge it is 

 usually replaced by a series of spines. Posteriorly it has about the same width as 

 in D. bicornis, but is ornamented with radial furrows instead of being plain. 



Formation and locality.— Middle third of the Trenton shales (Rhinidictya bed), Minneapolis, Minn. 



