American Palaeozoic Bryozoa. 141 



The jenus includes the following described species: Chaztetes granu- 

 liferus, Ulrich (Trenton); C. gracilis, James (Cin. gr.), Trematopora 

 annulifer, Whitfield (Cin. gr. ) ; and M . (Calamopora) tumida, Phillips, 

 and var. miliaria, Nicholson (Carboniferous). Besides these I have 

 one species from the Cincinnati Group, and two from the Sub-carbon- 

 iferous strata of Kentucky, which are as yet undescribed. In. i?. gra- 

 cilis, James, and B. tumida, Phill., we have a slender ramose zoariuim 

 the surface of which is without "monticules," and, with the exception 

 of a few irregular "macula?," is covered uniformly by the calices of the 

 true cells, and a variable number of interstitial cells. In well-pre- 

 served specimens the cell-walls are usually studded by a large number 

 of small spines or granules. In longitudinal sections the walls of the 

 tubes are very thin in their "immature'' portion, and remarkably thick- 

 ened in the cortical or "mature'' region of the branch. In neither 

 species are the diaphragms numerous. In tangential sections of both 

 species, the tube orifices are surrounded by a laminated ring, and the 

 intervening spaces are occupied by a few similarly constructed inter- 

 stitial tubes, and more or less numerous spiniform tubuli. 



Callopor a punctata, Hall, a Sub-carboniferous form, has characters 

 that are very distinct from G. elegantula, Hall, the type of the genus 

 Callopora, and I here propose the generic name Leioclema for the 

 species. 



The genus may be briefly characterized as follows: 



Leioclema, nov. gen. 



Zoarium ramose, branches slender, smooth, and sometimes hollow. 

 Cell apertures small, rounded, and with two or three series of subangu- 

 lar interstitial cells surrounding them. Longitudinal sections show 

 the tubes in the axial portion of the branch to be thin-walled, and 

 crossed by remote diaphragms. In the peripheral region the inter- 

 stitial tubes and spiniform tubuli are developed in great numbers. 

 The walls of all the tubes are much thickened, and the diaphragms in 

 the interstitial tubes are straight and remote, while in the true tubes 

 they appear to be wanting. In tangential sections the visceral cavity 

 of the proper zooecia is often indented by the encroachment of the rather 

 large spiniform tubuli, of which there are, in the type species, from 

 four to seven around the orifice of each tube. The interstitial 

 tubes are small, and of irregular shape ; two or three rows occupy each 

 intertubular space. 



Type, Callopora punctata, ? Hall. (PI. VI., figs. 1, la.) 



