Genera of the XoRxn American Palaeozoic Bryozoa. 537 



CosoiNiuM, Keyserling. 

 (Geognost. Beobacht., p. 192. 1846.) 



Type, Coscinium Cyclops, Keyserling. 



(Plate 13, figs. 8-12; pi. XIV, fig. 1.) 



Original diagnosis. "Lobed expansions in the form of a leaf, 

 consisting of two mutually applied strata, whose free planes ex- 

 hibit free pores quincuncially arranged so that on a cross fracture 

 of the leaf are seen the tubular oblique cells, biserially distributed 

 on either side, quite the same as in Esohara ; but here the foli- 

 aceous expansions are perforated by a regular series of holes as 

 in Adonea crihriformis, from which it varies, however, in the 

 want of an articulated stipe. Oar genus coincides also with 

 EscHARA in the character of the intercellular substance, which is 

 permeated by capillary tubules. This substance fills up with 

 age ; the holes likewise, which are then distinguished as spaces 

 without cells." 



The fronds of this genus very closely resemble those of Cos- 

 cinella, but differ in the absence of interapertural pits, and in 

 the presence of pseudosepta and lunaria. 



COSCINOTRYPA, Hall. 



(Report of N. Y. State Geologist for 1885 ; advance sheets Expl. 

 of Plate XXIX. 1886.) 



Type, Coscinoirypa crihriformis, Hall. 

 (Plate 13, figs. 1-7.) 



Zoarium consisting of explanate fronds, celluliferous on both 

 faces, with perforations or fenestrules at varying distances from 

 each other. At irregular intervals the surface is raised into 

 angular folds or plications, which continue growth in the same 

 manner as and at right angles to the parent frond. These in 

 turn give rise to similar elevations, the frond forming a very 

 irregular mass ; cell apertures arched and triangular, usually 

 irregularly disposed, but sometimes alternating and subimbri- 

 cating. The apertures adjacent to the fenestrules radiate from 

 them ; cells with two closely disposed, parallel pseudosepta, 

 which form a lunarium at the cell aperture, which consists of 

 strong crescentic denticulations. The fenestrules, in size and 

 distance from each other, are extremely variable. 

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