29G 



slight thickening of the walls, and the origination of an abundance of beaded 

 mesopores mark the initial periphery zone. A few thin diaphragms occur 

 in some of tlie zoecial tubes in the mature region and in others they are 

 absent. A distinct median lamina separates the zoecial walls. 



Occurrence : Pierce limestone, Murfreesboro, Tennessee. 



Holotype : 44708, U. S. Nat. Mus. 



Genus Diplotrypa Nicholsmh. Genotype: Favosites petropolitanus Pan- 

 der. Diplotrypa Nicholson, Pal. Tab. Corals, 1879, pp. 101, 155. Ulrich, 

 Jour, Cincinnati Soc. Nat. Hist, 5, 1882, p. 153. Foord, Contr'. Micro-Pal. 

 Cambro-Sil.. 1883, p. 13. Roemer, Leth. geog., 1, Leth, Pal., 1883, p. 472. 

 Miller, N. A., Geol. Pal., 1889. p. 187. Ulrich, Geol. Surv. Illinois, 8, 1890. 

 pp. 378, 457. Rominger, Amer. Geol., 6, 1890, pp. 116-119. Ulrich, Geol. Min- 

 nesota, 3, 1893, p. 285: Zittel's Textb. Pal. (Engl, ed.), 1896, p. 275; also 

 (not Ulrich) p. 104 (in part). Nirklos and P.asslor, Bull. U. S. Geol. Surv., 

 173, p. 36. Bassler, Bull. U. S. i'.w.]. Surv.. -JifJ. 1906, p. 47; Zittel-East- 

 man Textb. Pal., 1913, p. 33S ; Bull. V. S. Xat. Mus., 77, 1011, pp. 312, 313. 

 Callopora (not Hall) Dyhouski, Du Chaetetiden d. Ostb. Silur.-Form., 1877, 

 p. 106. 



The zoarium of Diplotrypa is massive, or discoid and generally free, con- 

 sisting of large prismatic zoecial tubes with thin walls. Mesopores are al- 

 ways present, but variable in number and size. Complete, horizontal dia- 

 phragms are present in both the zoecia and mesopores. Acanthopores are 

 wanting. 



Diplofri/pa catcnuJala ii. up. Plate X, Figs. 6-7. Zoarium massive, dis- 

 coid, 21/2 to 4 cm. in diameter and 1/2 to 214 cm. in thickness. The base is 

 circular, covered with thin concentrically vvriidvled epithelium. The zoecial 

 apertures are large and polygonal ; 4 to 41/2 in 2 mm. Mesopores are few 

 and of various shapes and sizes. 



In the longitudinal section the tube-walls are thin and beautifully crenu- 

 lated. The mesopores originate as catenated chambers, enlarging and de- 

 veloping into tubes similar to zoecia as they approach the periphery. The 

 diaphragms of the zoecia are spaced from 2 to 4 tube diameters apart in 

 the immature region and about one tube diameter apart in the mature zone. 

 In the mesopores diaphragms are present at the constrictions. 



The form of the zoarium, the large zoecia, crenulated walls and Irregu- 

 larly beaded me.sopores are a group of characters that distinguish this 

 species from any other species of the genus. 

 Holotype : 44658 U. S. Nat. Mus. 



Occurrence : Pierce limestone, Murfreesboro, Tennessee. 

 Genus Stromatotrypa Ulrich. Genotype : Stromatotrypa orata Ulrich. 

 Stromatotrypa Ulrich, Geol. Minnesota, 3, 1893, p. 301. Miller, N. A. Geol. 

 Pal., 2d App., 1897. p. 758. Nickles and Bresler, Bull. U. S. Geol. Surv.. 173, 

 p. 35. Grabau and Shimer. N. A. Index Fossils, 1. p. 137. 



Zoaria consist of laminated expansions growing upon foreign bodies, and 

 of globuler masses in which the zoecial tulies radiate from a small base 

 covered with epitheca. The zoecia have thin walls and are cx'ossed by few 



