246 



BULLETIN 11, UNITED STATES NATIONAL MUSEUM, 



(I 



Fig. 140.— EErooTRTPA exigua. a, geoup of 



FRAGMENTS, NATURAL SIZE; 6 AND C, TWO OF 

 THEM, X9. NeMATOPOEA BED OF THE LOWER 



Trenton limestone, near Cannon Falls, 

 Minnesota. (After Uleich.) 



Considering the small size of the branches, the zooecia are large. Their apertures are 

 oblique, but not excessively so, subequal, and arranged in both longitudinal and 

 diagonal series, the former Avith eight in 3 mm., predominating in the small speci- 

 mens, and the latter in the larger. At 

 the lower end of each aperture the wall 

 is usually raised into a spine-Hke promi- 

 nence. In vertical sections the greater 

 part of the branch is seen to consist of 

 comparatively large and nearly or quite 

 vertical tubes, intersected here and there 

 by a diaphragm. The peripheral region 

 is exceedingly short and abrupt. 



Occurrence. — This neat little 

 species is very abundant in the 

 Nematopora bed of the Lower 

 Trenton at Cannon Falls, Minne- 

 sota; it also occurs in the lower 

 part of the Trenton limestone at 

 Trenton Falls, New York, and Chimney Point, Vermont. The spe- 

 cies is represented in the Russian collections by a number of exam- 

 ples from the Jewe limestone (Dl), Baron Toll's estate, near Jewe 

 (Cat. No. 57219, U.S.N.M.). 



British Museum, one specimen from Jewe limestone, Baron Toll's 

 estate. 



Genus LIOCLEMA Ulrieh. 



Leioclema XJlrich, Journ. Cincinnati Soc. Nat. Hist., vol. 5, 1882, pp. 141, 154. — 



Miller, North Amer. Geol. and Pal., 1889, p. 310. — Ulrich, Geol. Surv. 



IlUnois, vol. 8, 1890, pp. 376, 425. 

 Lioclema, Nickles and Bassler, Bull. 173, U. S. Geol. Surv., 1900, p. 33. — 



Ulrich and Bassler, Smiths. Misc. Coll., vol. 47, 1904, p. 38. — Bassler, 



Bull. 292, U. S. Geol. Surv., 1906, p. 32. 



This genus has its best representation in the Devonian, although 

 a fair number of species is known from both Silurian and Mississippian 

 deposits. Hitherto the oldest known species has been Lioclema 

 wilmingtonensis Ulrich, from the earliest Silurian (Richmond) forma- 

 tion of Illinois. The following new species gives a greater antiquity 

 for the genus, although it occurs in the same faunal region as the 

 Richmond form. 



The form of growth in Lioclema varies from the incrusting through 

 the explanate and solid massive to the ramose. The batostomelloid 

 character of the fused walls is less evident in this genus, particularly 

 in the earher forms, such as the one described below. The numerous 

 acanthopores inflecting the zocecia and the isolation of the sparsely 

 tabulated zooecia by closely tabulated, angular, thin-walled mesopores 

 are other characters which will aid in the recognition of the genus. 



Genotype. — Callopora punctata Hall. Mississippian (Keokuk and 

 Warsaw) strata of the Mississippi Valley. 



