36 The Ottawa Naturalist [June-July 



Station 509 Trenton limestone, about fifteen feet above its base, 

 along course of small brook tributary to Bayfield Bay. 

 Lot 1, south, Con. X., Wolfe Island. 



Description of Species. 



Phyllum Molluscoidea. 



Class Bryozoa. 

 Order Trepostomata. 

 Family Halloporidae. 

 Genus Hallopora Bassler. 

 HALLOPORA VARIA n. sp. 

 Plate I. figs. 3-7. 

 Zoarium composed of subcylindrical branches, 5 to 8 mm. in 

 diameter, bifurcating at frequent intervals; one fragment 22 mm. long 

 has given off five branches. Surface of branches gently undulatorv 

 but without conspicuous monticules or maculae. Zooecial apertures 

 angular, about 10 in 3 mm.; walls ridge-like and thin; mesopores very 

 few, generally occurring only in limited areas of the surface. 



Tangential sections show the zooecia to be everywhere in contact 

 with each other except in certain spots where small mesopores occupy 

 the angles between zooecia. Vertical sections in the axial region dis- 

 play two sets of tubes, the smaller of which represents mesopores, and 

 the proximal portion of zooecia; in the larger tubes the diaphragms 

 are from 0.2 to 0.5 mm. apart, with an average distance of about 0.35 

 mm.; this is slightly greater than the diameter of the tubes, which 

 almost invariably falls between 0.28 and 0.55 mm. The smaller tubes 

 contain diaphragms which are only 0.11 to 0.17 mm. distant, generally 

 about as far apart as the diameter of the tube. In the peripheral zone 

 the tubes bend rather abruptly and proceed toward the surface with 

 only slight obliquity; here the diaphragms are from one-third to one- 

 half the diameter apart. 



This form is most nearly related to H. angularis (Ulrich). The 

 chief differences are the larger size of the branches, the greater dis- 

 tance between diaphragms in the axial portion of zooecial tubes, and 

 the less pronounced crowding of diaphragms near the apertures. 

 Horizon and locality: Lower Trenton Limestone; Wolfe Island, 

 Ontario, (Stations 226 and 509). 



HALLOPORA OBLIQUA n. sp. 

 Plate 1, figs. 8-11. 

 Zoarium ramose, composed of slender cylindrical branches, 2 to 

 4 mm. in diameter, bifurcating at comparatively remote intervals; sur- 

 face of branches slightly undulatorv but without conspicuous monti- 

 cules or maculae. Zooecial apertures polygonal, with thin smooth 

 ridge-like walls, about eleven in 3 mm. Mesopores open at the surface, 

 polygonal in cross-section, about as numerous as the zooecial apertures. 



