238 PALEONTOLOGY OF NEW YORK. 



cose IN I UM, Keyserling. 1846. 



COSCINIUM STRIATUM, 11. Sp. 

 PLATK LXIV, FIGS. 18-16. 



ZoARiUM consisting of an explanate frond, celluliferous on each face, with oval or 

 circular perforations or fenestrules, at somewhat regular distances ; length of 

 fenestrules about 2 mm., width from 1.25 to 2 mm., generally distant trans- 

 versely about 3 mm., longitudinally 4 mm. ; transverse section between the 

 fenestrules, broadly lenticular or acutely oval, greatest thickness 1.75 mm. 

 Mesotheca thin, marlted by arching undulations of growth and also by longi- 

 tudinal striations, caused by the recumbent cell tubes. Cells tubular cylin- 

 drical, for about one-half their length parallel with, and resting upon the 

 mesotheca, then abruptly bending and continuing at right angles to the axis, 

 opening directly outward. Intercellular tissue vesiculose, vesicles minute, 

 irregularly disposed, or regularly superimposed and having the appearance 

 of septate tubuli. Cell apertures broadly oval, length .30 mm., width 

 .20 mm., or more, irregularly disposed, generally separated by a little less 

 than the diameter of an aperture. Peristomes thin, slightly and equally 

 elevated, having on one side two minute denticulations, which in the course 

 of growth, form two parallel striations along the inner face of the cell wall. 

 In the cell apertures adjacent to the fenestrules the denticulations always 

 proceed from the external margin. There is a non-celluliferous space of .75 

 mm. wide bordering each fenestrule. Interapertural space slightly con- 

 vex, and in common with the non-celluliferous space around the fenestrules 

 is striated ; striae fine, sinuous, interrupted, from three to six between adja- 

 cent cell apertures. Sometimes when the frond is worn so that the strisB 

 are obsolete the vesicles are externally visible, appearing as minute angular 

 pits. 



This species may be distinguished from the ordinary forms of Coscinium by 

 the striated surface, the size and form of the fenestrules, and their distance from 

 each other. In gener.-il aspect it closely resembles Coscinella elegantula, but it 



