BRYOZOA. 369 



Types: D. trentonense n. sp.,* from the Trenton group of 

 NV\\ York, and D? sparsum (Trematopora sparsa Hall) from 

 the Niagara group. 



MITOCLEMA Ulrich. Zoaria ramose, slender, subcircular in 

 transverse section. Zooecia tubular, very long, gradually diverg- 

 ing in all directions from an imaginary axis. Apertures prom- 

 inent, circular, arranged in transverse series around the stems. 

 AYalls thin. 



Type: M. cinctosum Ulrich. Range, Chazy. (For internal 

 structure see PI. LIII). 



PROTOCRISINA n. gen. Zoaria ramose, celluliferous on one side 

 only. Zooecia subtubular, with prominently exerted circular aper- 

 tures. Reverse finely grano-striate. Small pores, apparently 

 communicating with the interior of the zooecia, are rather irre- 

 gularly distributed over both sides of the branches. Axis thin, 

 cruciform in transverse section. External walls thick. 



Type: P. exigua n. sp. (PI. LIII, fig. 11-llc). Range, Tren- 

 ton and Cincinnati. 



Sub-order TREPOSTOMATA Ulrich. 



Family MONTICULIPORID.E Nicholson. 

 (Emended and restricted.) 



Zoaria massive, discoid or lamellar, ramose or bifoliate. 

 Zooecia with thin and probably minutely perforated walls, the 

 peculiar granular structure exhibited in thin sections being 

 strongly indicative of an originally porous condition. Aper- 

 tures polygonal, rounded, or irregularly petaloid. Mesopores 



* DipJocleina trentonense TTlr. As this spec-ies has not yet been described, I append 

 here a brief diagnosis of its characters. Zoarium slender, ramose, dividing dichoto- 

 mously at an angle varying from 70 to 90 degrees; intervals between divisions, 5 mm., a 

 little more or less. Branches 0.55 mm. wide, 0.35 to 0.4 mm. thick. Zooecia tubular, in 

 tangential sections faintly moniliforni near their origin. Apertures slightly constricted, 

 p eminent, circular. 0.1 mm. in diameter, in three or four rows on each side of the 

 branch; generally arranged in oblique rows, less commonly transversely; at other times 

 irregular, four or five in 2 mm. measuring longitudinally; transversely the interspaces 

 are shorter. 



The species is Quite common at Trenton Falls, N. Y. The internal structure of i 

 D. trentonense and D. sparsum is figured on PL LIII. 



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