156 BULLETIN 11, UNITED STATES NATIOlSrAL MUSEUM. 



Illinois. These particular strata are now known as the Girardeau 

 limestone and are of Richmond age. The Minnesota specimens 

 identified by Ulrich with Nematapora delicatula were found in the 

 Nematopora bed of the lower Trenton. While the specimens in 

 these rather widely separated horizons are quite similar, close com- 

 parison reveals sufficient differences to justify their recognition as 

 separate species. The similarity of the two forms is only another 

 example of the close relationship between the Black River, early 

 Trenton, and Richmond faunas, a fact which has been noted at 

 numerous places in this work. 



Illustrations of both Nematopora delicatula and N. consueta are 

 shown in figure 76, and upon comparing them the latter species is 

 found to have apertures slightly larger, more rounded, and a trifle 

 exsert, although a more obvious difference lies in the greater distance 

 between its zooscial openings. 



Occurrence. — The American types of N. consueta were found in the 

 Nematopora bed of the lower Trenton near Cannon Falls, Minnesota. 

 In Russia, specimens are not uncommon in the Kuckers shale (C2), 

 Baron Toll's estate, in Esthonia (Cat. No. 57250, U.S.N.M.). 



British Museum, one specimen from the Kuckers shale. Baron Toll's 

 estate. 



NEMATOPORA OVALIS Ulrich. 



Text fig. 77. 



Nematopora ovalis Ulrich, Journ,. Cincinnati Soc. Nat. Hist., vol. 12, 1890, p. 



197, fig. 21; Geol. Nat. Hist. Surv. Minnesota, vol. 3, pt. 1, 1893, p. 204, pi. 



3, figs. 24, 25. 

 Nematopora quadrata Ulrich, Geol. Snrv. Hlinois, vol. 8, 1890, p. 644, pi. 29, 



figs 12-12c. — Simpson, Fourteenth Ann. Rep. State Geologist of New York 



for the year 1894, 1897, p. 553, figs. 124, 125. 



The surface characters of this fine species are so distinct from other 

 forms of Nematopora that there should be little difficulty in its identi- 

 fication. Ulrich's diagnosis of the species is concise and applies 

 equally well to the Russian specimens. 



Original description. — Zoarium ramose; branches bifurcating at intervals of about 

 2 mm., 0.3 to 0.4 mm. in diameter, sub quadrangular or pentagonal in cross section, 

 each face with a row of zooecia. Zooecial apertures direct, very large, oval, nearly 

 0.3 mm. long by 0.15 mm. wide, inclosed by a sharply defined peristome. A short 

 ridge joins the peristomes of each row of apertures, and longitudiaally divides the 

 concave spaces between the ends of the apertures. These spaces are larger in the sub- 

 quadrate examples than in those having five rows of zooecia. They also have the thin 

 ridge that bounds each face more distiact from the elevated margins or peristomes of the 

 zooecial apertures, which, in the pentagonal specimens, to a large extent also form the 

 border of the faces. Longitudinal interspaces generally shorter than the length of 

 the zooecial apertures; about five of the latter in 2.5 mm. 



Occurrence. — The Minnesota types of the species occurred in the 

 Nematopora bed of the early Trenton near Cannon Falls. Specimens 



