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Holotype: 244-17. Indiana University. 
Genus Mesotrypa Ulrich. Genotype; Diplotrypa infida Ulrich. Diplo- 
trypa (in part Nicholson, Paleozoic Tabulate corals, 1879, p. 312; genus 
Monticulipora, 1881, pp. 101, 155. Ulrich, Jour. Cincinnati Soc. Nat. Hist., 
5, 1882, p. 153. Foord, Contr. Micro-Pal. Cambro-Sil., 1883, p. 18. Ulrich 
Geol. Sury. Illinois, 8, 1890, p. 378. 
Mesotrypa Ulrich, Geol. Minnesota, 3, 1893, p. 257. Nickles and Bassler, 
Bull. U. S. Geol. Sury., 173, p. 30. Bassler, Bull. U. S. Geol. Sury., 292, 1906, 
p. 27. Grabau and Shimer, N. A. Index Fossils, 1, 1907, p. 130. Hennig, 
Archiy. fur Zool., 4, No. 21, 1908, p. 29. Bassler, Bull. U. S. Nat. Mus., 77, 
1911, p. 196. 
Zoarium hemispheric, conical, discoidal or inecrusting. It is generally 
free with an epithica covering the base; zooecia are polygonal or circular 
with curved, and sometimes funnel-shaped diaphragms, which are probably 
modified cystiphragms; zooecia more or less separated by angular meso- 
pores, which become smaller with age, and are intersected by numerous 
diaphragms; acanthopores generally present. 
Mesotrypa crustulata n. sp. Plate V, Figs. 5-6. The zoarium of this spe- 
cies forms incrusting expansions about 2 mm. in thickness. In the type 
specimen the zoarial mass consists in part of superimposed layers and at- 
tains a height of 8 to 10 mm. On the surface small low monicules of large 
zoecia and numerous mesopores are irregularly distributed, varying from 1 
to 3 mm. apart. In places the surface rises into conical-like tubercles .5 to 
1 mm. high, and from 8 to 12 mm. apart. 
The zoecia are thick-walled at the surface, circular, regularly arranged, 
and in contact on 3 or 4 sides; 74% to 8 intermonticular and 54% monticular 
zooecia occur in 2 mm. 
The acanthopores are small, inconspicuous, and unequally distributed, 6 
to 7 about a zooecia in some areas and in others no acanthopores are pres- 
ent. 
Mesopora are abundant; more numerous at the base than in the mature 
zone. Diaphragms are closely set; 13 to 15 in the distance of one mm. 
The diaphragms in the zooecia are in rather definite parallel transverse 
horizons, separated by a distance equal to 1% to 2% tube diameters. Two 
to six diaphragms 4% to 4% tube-diameters apart are present in each zooecia 
at the elevation of the common horizons. Curved and cystoid diaphragms 
occur in the mature part of the zooecial tube only. 
The segregation of the small and inconspicuous acanthopores into areas 
closely associated with the monticular zooecia, the zonal arrangement of the 
diaphragm and the localization of the curved and cystoid diaphragms in the 
peripheral portion of the zoarium are the conspicuous differentiating char- 
acters of the species. 
Occurrence: Pierce limestone, Murfreesboro, Tennessee. 
Holotype: (92) U.S. Nat. Mus. 
Mesotrypa dubia. n. sp.. Plate VI, Figs. 1-2. Zoarium consists of thin 
expansions 2 mm. in thickness. Small inconspicuous maculae, consisting 
