American Palaeozoic Bryozoa. 



157 



layer, or numerous superimposed layers. Tubes short, with the aper- 

 tures rounded, and more or less oblique. Interstitial cells numerous, 

 and in the matured state covered by a thin membrane. Cincinnati. 



Cheiloporella, Ulrich. — Forming heavy crusts, or rising upward into 

 flabellate fronds. Tubes long, traversed by few straight diaphragms. 

 Cell-apertures ovate. Interstitial cells numerous. Cincinnati. 



Crepipora, Ulrich. — Usually incrusting, sometimes irregularly ra- 

 mose with hollow branches. Cell-apertures very little oblique, rhom- 

 boidal, with a slightly projecting -'lip." Interstitial cells usually 

 restricted to the "maculae," which are distributed at rather regular 

 intervals over the surface. Two delicate longitudinal lamellae are 

 present in each tube. Diaphragms are developed in moderate number. 

 Cincinnati. 



JEridopora, Ulrich. — External characters as in C eramoporella. Long- 

 itudinal sections demonstrate that the intertubular spaces are occupied 

 by a well developed vesicular tissue. Sub-carboniferous. 



Sub-order Cheilostomata, Busk. 

 Fam. Membraniporidce, Busk. 



t Paleschara, Hall. — Zoarium incrusting; tubes very short. Cell- 

 apertures direct, angular, and more or less oblong. Cincinnati to 

 Lower Helderberg. 



A few American Palaeozoic genera of Bryozoa have been omitted 

 from the above classification, because I have not yet been able to give 

 them the attention required for a full elucidation of their characters 

 and affinities. 



DESCRIPTIONS. 



Genus Berenicea, Lamx. 



The dividing lines between the genera Berenicea, Proboscina, and 

 Stomatopora, are, especially among Palaeozoic forms, not strongly 

 marked, since it is mainly in their mode of growth that they differ. 

 As, however, these generic names are convenient in classifying the 

 numerous species placed under each by such authorities as Busk, 

 Haime, and Reuss, 1 have thought it proper to recognize the genera in 

 classifying the Lower Silurian species. 



Berenicea primitiva, n. sp. (Plate VI., fig. 4.) 

 Zoarium attached to foreign bodies, and forming small subcircular 



