﻿ULRICH BASSLER] REVISION OF PALEOZOIC BRYOZOA 33 



masses, _' to 4 nun. in diameter, by growth around associated smaller 

 organisms. Occasionall) the zoaria are discoid or irregular. The 

 acanthopores are strongly developed and many specimens bristle 

 with them. Zocecial apertures rounded or subangular, 9 [O in 2 mm. 



Occurrence. — Very abundant in the uppermost stratum of the 

 Warren beds of the Cincinnatian. The types are from Middletown, 

 Ohio; but Clarksville, Oregonia, Lebanon, and other localities in 

 southwestern ( )hio furnish exposures where the species can be found 

 in abundance. 



Cat. Nos. 43,194-43,196, U. S. X. M. 



Genus Stigmatella new genus 

 Zoarium variable, ranging from incrusting to irregularly massive 

 and ramose. Zocecia angular, rounded, or irregularly petaloid, the 

 shape depending upon the presence (or absence ) of mesopores and 

 the number of acanthopores. Typically the zoarial surface exhibits 

 at regular intervals maculae or spots composed of mesopores, 

 although in some species the usual monticules or clusters of large 

 cells occur. Acanthopores always present but variable in number, 

 intermittent, developed chiefly in narrow zones, sometimes inconspic- 

 uous but more often so numerous as to give the surface a decidedly 

 hirsute appearance. Mesopores, when present, developed in mature 

 region only, their number being variable even for the same species. 



The zocecial tubes have thin walls in the axial region and these 

 become but slightly thickened in the peripheral region wdiere a few 

 unusually delicate diaphragms are inserted. In vertical sections the 

 walls exhibit at rather regular intervals in the peripheral region thick- 

 ening's somewhat similar to those occurring in Stenopora. These 

 thickenings occur approximately at the same height in the walls, and 

 tangential sections through these zones give the full development of 

 acanthopores. Minute structure of walls as shown in tangential sec- 

 tions, of the type that characterizes the Heterotrypida. 



Genotype. — Stigmatella crenulata new species. Richmond forma- 

 tion, Ohio. 



This genus is proposed to receive a few species which from time to 

 time have been referred to Montkulipora, Leptotrypa, and Mono- 

 trypa by authors, for the new forms here described and finally for 

 several additional undescribed species whose publication had to be 

 deferred on account of a lack of space. Although (littering widely 

 in zocecial habit, these species seem to form a natural group of the 

 Heterotrypidcc. distinguished by the periodic thickening of the walls 

 of the zocecial tubes and the accelerated development of the acantho- 



