16 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxx. 



Although the original description of this fine species is incorrect in 

 several details, the study of the types shows that it was correctly 

 identified and well illustrated b}^ Ulrich in 1882." 



The zoarium is jointed, but specimens showing the segments still in 

 connection are not common. The segments are very slender, straight, 

 needle-shaped rods, about 5 mm. in length, slightly expanding toward 

 the obtusely rounded upper extremit}'. The latter articulates with 

 the pointed lower ends of generally two succeeding segments, the 

 complete zoarium appearing to consist of extremely delicate and regu- 

 larly bifurcating branches. Cross sections of a segment are subquad- 

 ranguhir in shape, three of the sides being concave and equal in width, 

 while the fourth side is slightly convex and half again as wide. Each 

 of the three equal sides bears a row of zocecia, while 6 to 8 longitudi- 

 nal striie mark the fourth side. The zooecial apertures are oval, and 

 when perfect have a delicate and prominent equall}'' elevated rim; 9 

 zooecia in 2 nmi. • 



The small slender segments of ^1. tenuis with the three equal cellu- 

 liferous sides and the broader, striated, noncelluliferous fourth side 

 are so ditterent from the zoaria of all other bryozoa in the Cincin- 

 natian series that comparison is not necessary. 



Occurrence. — Not uncommon throughout the Eden shale at Cincin- 

 nati and vicinity. James's type is from the lower division (Economy 

 member) where specimens are particularly abundant. 



ASPIDOPORA CALYCULA (James.) 

 Plate I, ligs. 8-10. 



Lichcnalld f cabjoila James?, Catal. Fosp. Cincinnati Group, 1871, p. 5 (not 



defined ) . 

 Chirtetes f calynduH James, Introd. Catal. Foss. CiiH'imiati Croup, 1875, p. 1. 

 Monticulipora {Diplotrypa) calycula Nicholson, Genus Monticulipora, 1881, p. 



165, pi. IV, figs. 4-46. 

 J/on//fw/(/)orac«///cu/« James and James, Jour. Cincinnati Soc. Nat. Hist., X, 1888, 



p. 167.— J. F. James, Jour. Cincinnati Poc. Nat. Hist., XVI, 1894, p. 184. 

 Asjndoponi cab/cula Ulrich, Geol. and Nat. Hist. Surv., Minnesota, Final Rept., 



Ill, Pt. 1, 1893, p. 255. 



Most of the characters of this species have been so well described 

 and illustrated by Nicholson that its identification is a matter of little 

 difiiculty. New figures of the internal structure are introduced here 

 parti V to show the identity of Jumes's types with the form described 

 b}" Nicholson, but mainly to give a better illustration of a vertical 

 section than has been published heretofore. In the vertical section 

 figured b}^ Nicholson the zoarium is cut in such a way that a false idea 

 of the internal features is presented. Such sections, in order to bring 

 out the essential characteiv<, should cut the zoarium at right angles to 

 the growing edge. A. ca/z/cula, when sectioned in this way, shows 



«Geol. and Nat. Mist. Surv. Minn., Final Report, III, Pt. 1, 1893, pi. in, fig. We. 



