194 



Cincinnati Society of Natural History 



cycle more oblique than the others, and situated very near the upper 

 extremity of the segment. Angles of segments, peristomes of the 

 oval zooecial apertures, and longitudinal interspaces between them, 

 more or less regularly papillose. Secondary segments 1.5 to 1.8 

 mm. long, about 0.45 mm. in diameter, generally with only three 

 cycles of zooecia, and without articulating sockets. Otherwise 

 very similar to those of the primary set. The papillose ornamenta- 

 tion of the surface is, however, generally more regular. 



The neat little detached segments of this species are rather 

 plentiful on the limestone slabs of the lower portion of the Tren- 

 ton Shales, near the State University at Minneapolis, Minn. A 

 larger segment of another species that is more closely related to 

 A. pulchellum, Billings, is occasionally found with them. It is not 

 at all likely that they will be confounded. The next described 

 species (A. an?iatu?ii) is a nearer relative, but readily distinguished 

 by its larger segments and prominently produced lower border of 

 its zooecial apertures. 



ARTHROCLEMA ARMA'lUM, n. sp. 



mm 



mm 



rffl 



Fig. 19.— Arthroclema armatum, n. sp. a, large segment of the primary series, showing 

 a sharply defined articulating socket. 6, opposite side of another segment of the pri- 

 mary set. c, a broken segment of the secondary series, the upper half being preserved. 

 d, another, but entire, segment of the secondary set. e, vertical section of a secondary 

 segment, showing central axis and form of zooecia. /, transverse section of primary 

 segment, g and h, two tranverse sections of secondary segments, one with six the 

 other with seven rows of zooecia. All the figures are magnified eighteen diameters. 



