Maryland Geological Survey 277 



Petalotrypa has the wall structure of the Integrata/ whereas the proposed 

 Diplostenopora is, like the rest of the Batostoraellidai to which family it 

 is referred, distinctly a representative of the Axnalgamata. Furthermore, 

 Petalotrj'pa has straight and complete diaphragms while those found in 

 Diplostenopora sUuriana are centrally perforated. 



Diplostenopora siluriana (Weller) 

 Plate XLV, Figs. 3-6 ; Plate XLVIII, Figs. 1-3 ; Plate LII, Figs. 3, 4 



Escharopora siluriana Weller, 1903, Paleont. N. J., vol. iii, p. 225, pi. xviii, 

 figs. 6, 7; pi. xix, figs. 8, 9. 



Description. — Zoarium of flattened fronds, which have subparallel 

 edges, are bifoliate and branch dichotoraously at rather regular intervals 

 of about 1..5 cm.; angle of bifurcation about 7'5°. The largest specimen 

 seen is fragmentary but branches twice and has a height of 4.5 cm. and 

 average width of 7 mm. Edges of branches thin and sharp in growing 

 examples but somewhat rounded in more mature specimens, apparently 

 never developing a nonporiferous border. Surface usually smooth, but 

 occasionally, in young specimens especially, having the cluster of larger 

 cells raised into low rounded monticules. 



Zocecial apertures rounded, enclosed by fairly thick walls which rise 

 ridge-like ?o that the crest forms a polygonal outline about the apertural 

 slope. Mesopores few and confined almost entirely to the maculae. Acan- 

 thopores not observed at the surface. In thin sections they are few and 

 small, a single one being occasionally found in the angle between several 

 adjoining zooecia. Eight zooecia in 2 mm. 



The internal structure is shown clearly on pi. xlv, and it is therefore 

 thought unnecessary to describe it in further detail. Figs. 5 and 6 show 

 the most important of the specific as well as generic characters, namely, 

 the bifoliate structure of the zoarium, the perforated diaphragms and 

 the absence of constrictions in the zooccial walls characterizing the other- 

 wise similar stcnoporoids. 



' The Trepostomata have been classified by the present writers in two large 

 divisions, the Integrata in which the walls of adjoining zooecia are distinct and 

 separated by a dark divisional line and the Amalgaviata with adjoining walls 

 fused. 



