19 



Calloporella vacua, sp. nov. 

 Plate I, Figures 5 and 6 



This species occurs in the Strophomena varsensis zone of the Erindale 

 formation, on Cooksville creek. The zoarium is discoidal, with a convex upper 

 surface and a concave lower surface, as in Mesotrypa patella (Plate V, Figure 9). 

 The lower surface is covered by an epitheca. The discs measure about 15 mm. 

 in diameter and are 2.5 mm. thick at the centre. The character of their surfaces 

 can not be ascertained as the apertures of the tubes are filled with limestone. 



The zooecial tubes are of average size and thin-walled, as seem in tangential 

 sections. Mesopores are large, but are less numerous than in other members 

 of the genus, there being usually only three or four in contact with each zooecial 

 tube. This disposition of the mesopores allows adjacent zooecia to touch one 

 another at many points. Acanthopares are absent. 



In vertical sections, it is seen that the mesopores and zooecial tubes alternate 

 with one another with considerable regularity. Diaphragms are crowded in 

 the mesopores, but the zooecial tubes have few or no diaphragms. The arrange- 

 ment of the bases of the alternating zooecia and mesopores is quite regular as in 

 Peronopora vera, Ulrich, as described by Parks and Dyer for specimens from the 

 Don River section at Toronto. The bases of the zooecia are small and 

 trapezohedral in shape, while the bases of the mesopores are larger and 

 hexagonal. 



C. vacua differs from any other member of the gerrus in the paucity of the 

 mesopores and in' the apparent lack of diaphragms in the zooecial tubes. The 

 latter feature is so marked that the reference of the species to Calloporella is 

 doubtful, as the genus is characterized by numerous diaphragms in the zooecial 

 tubes. On the other hand, there is no other described genus to which the form 

 could be more suitably ascribed. 



Locality. — Cooksville creek. 



No. 12149, Royal Ontario Museum of Paleontology. 



Hallopora aequalis, sp. nov. 

 Plate I, Figure 7; Plate II, Figures 1 and 2; Plate VII, Figure 15 



A species of Hallopora which differs from any previously described form is 

 well represented in the Streetsville and Erindale members ; it is ramose in growth 

 and rather large, the branches averaging seven millimetres in diameter. The 

 surface is smooth. The zooecial apertures are polygonal, somewhat variable 

 in size, and comparatively small, nine to ten occurring in two millimetres. 

 Mesopores are extremely few. 



In tangential sections cut from near the surface, the mesopores ares omewhat 

 more numerous than at the actual surface, there being on the average two or 

 three mesopores for every zooecial tube, but considerable portions of these 

 sections can be found in which mesopores are entirely absent. The mesopores 

 occur at the angles of the walls and are very often found in pairs. In deeper 

 tangential sections, the mesopores are more numerous, showing that they pinch 

 out on approaching the surface. In still deeper tangential sections, the meso- 

 pores are very numerous, entirely surrounding the zooecial tubes. 



Vertical sections demonstrate beautifully the manner in which the mesopores 

 pinch out on approaching the surface. In deeper parts of the zoarium they are 

 numerous, but outwards they grow smaller and finally disappear altogether 



