172 W. I. Robinson, 



trabecular structure which characterizes that genus; (2) the 

 presence of compact fibrous coenenchyma, forming the whole of 

 the corallum; (3) the presence of a definite system of ring-canals 

 and branches; (4) the presence of a well-developed basal 

 epitheca, which is unattached. 



The differences from Pleurodictyum are given as: (i) The 

 calices are low and vertical, not funnel shaped; (2) there is no 

 trace of tabulae or septal spines; (3) the corallum is unattached; 

 (4) there is no commensal vermiform body; (5) ring-canals are 

 present. Pleurodictyum resembles Vaughania, however, "in the 

 presence of intramural pores and of a concentrically striated 

 basal epitheca." 



The differences from Pakeacis are: (i) A much greater 

 number of calices; (2) the corallites not wedge-shaped, but 

 arranged with their walls perpendicular to the basal plate; (3) 

 the calices having (comparatively) narrow and polygonal walls 

 rising from the basal plate, and not excavated as circular pits in 

 the general mass of the corallum; (4) the absence of vertical 

 striae in the calices: (5) the regular arrangement of the 

 perforations to form ring-canals; (6) lack of attachment. 



Palceacis has similar pores. Microcyathus, which contains 

 species often referred to Palceacis, resembles Vaughania in the 

 compact calcareous matter in its walls, the wrinkled basal 

 epitheca (this however is not always present in Microcyathus) 

 and the presence of pores. These latter are more irregular in 

 the case of Microcyathus and cannot be as correctly defined as 

 a definite tubular system. Microcyathus has more rounded 

 calices and blunt spines which seem to represent septa. 



Genus Conopoterium Winchell. 



1865 Conopoterium Winchell. Proc. Acad. Nat. Sci. Phila., 

 Vol. XVII: no. 



This genus is doubtfully referred to the Leptoporidae, as it 

 exhibits some characteristics of the Favositidae and may represent 

 a transitional form. 



Original Description. — "Corallum compound, generally free, 

 sometimes adherent, but without a distinct base of attachment. 

 Cells somewhat crowded, rapidly enlarging, inseparable, with 

 only occasional and rudimentary diaphragms, and no radial 



