CORALS AND BRYOZOA. 239 



may easily be distinguished from that form by the oval cell apertures, the 

 presence of denticulations, and the absence of inter-apertural pits: the 

 peristomes, denticulations and absence of interapertural pits, distinguish it 

 from Coscinium cosciniforme. It is the only species of the genus at present 

 known, from the Upper Helderberg and Hamilton groups, having a distinctly 

 striated surface. 



Formation and locality. Hamilton group, Widder, Ontario, Canada. 



COSCINELLA, nov. gen. 



COSCINELLA ELEGANTULA. 

 PLATE LXIV, FIGS. 9-12. 



ZoARiUM consisting of an explanate frond, celluliferous on each face, with perfora- 

 tions or fenestrules at somewhat regular distances from each other, the whole 

 having the appearance of being composed of sinuous, anastomosing branches. 

 Base spreading, adhering to Cyathophylloid corals or other bodies ; pedicel 

 cylindrical, short, diameter about 18 mm. ; fronds large, fragments occurring 

 which have a length of 80 mm. and a width of 110 mm. The fenestrules 

 vary in form from circular to elongate-oval, length generally from 1.50 to 2 

 mm., width a little more than 1 mm., both larger and smaller fenestrules 

 occurring, usually distant about 3.50 mm. A transverse section of the frond 

 between the fenestrules is lenticular, greatest thickness 1.30 mm. The 

 mesotheca is very thin, marked by arching undulations of growth and also 

 by longitudinal striations, caused by the recumbent portion of tlie cell 

 tubes. Cells tubular, cylindrical, for one-half their length parallel with, 

 and resting upon the mesotheca, then abruptly bending and continuing 

 rectangularly to their former course, opening directly outward. Intercellular 

 tissue composed of tubuli, with very closely disposed septa, or of vesicles so 

 disposed that they have the appearance of septate tubuli. Cell apertures cir- 

 cular, diameter .25 mm., closely disposed, very frequently in contact, seldom 

 separated by more than one-half the diameter of an aperture, usually by not 

 more than one-third, generally irregularly disposed, but sometimes forming 



