72 CONTRIBUTIONS TO CANADIAN PALAEONTOLOGY. 



This species is thus denned in Dr. Rominger's work on corals : " Tubes * 

 oval, in chain-like, lateral conjunction, but these laminae are so closely 

 approximated, that no retiform loops are formed by them ; they come in 

 contiguity with each other from all sides, and leave only small, angular, 

 lacunose interstices in the corners of their intersection, which are not 

 larger than the tube orifices themselves. By this close approximation of 

 the tubes on all sides many of them become pressed into a polygonal 

 form and resemble a Favodtes, from which they differ, however, in the 

 absence of lateral pores. The diaphragms of the tubes are closely 

 approximated, flat, concave or convex in the same specimens. Their dia- 

 meter is about one and a half millimeter. Found in the Niagara group 

 along the outcrops of the Upper Peninsula, at the shore of Lake Michi- 

 gan. In a stratum of an outcrop at the mouth of Manistique River this 

 species is quite common." 



Halysites compacta occurs in Canada, as far as is now known, in the 

 Niagara formation at Lake Temiscaming, Ont., in the Guelph formation 

 at Gait, Elora and Hespeler, Cnt., and near Donald, B.C., in rocks of 

 Silurian age. The Guelph specimens in the collection of the survey were 

 seen by Dr. Rominger, who testified to the correctness of Mr. Whiteaves's 

 identification (vide op. cit. p. 2). Dr. Robert Bell in 1887 obtained 

 three specimens from Lake Temiscaming, one of which (Plate IV., 

 fig. 5) is identical with the type as figured by Rominger, and agrees at 

 all points with the specific description. Another (Plate IV., fig. 6) shows a 

 slight variation in that the corallites are not always in contact, there 

 being interspaces which are at times slightly larger than the corallites- 

 The third is similar to a number of specimens collected in 1893 and 1894 

 by Mr. A. E. Barlow, of this Survey, also at Lake Temiscaming, at a 

 locality about two miles distant from where Dr. Bell collected his, which 

 although belonging most probably to Dr. Rominger's species, still depart 

 from this typical form in so decided a manner as to be worthy of notice. 

 A single specimen was also collected in 1885, by Prof. A. P. Coleman, on 

 the N. E. side of the Columbia River, near Donald, B.C., from rocks of 

 Silurian age, and another was obtained by J. B. Tyrrell, in 1890, in 

 rocks of the same age at the foot of Grand Rapids, near the mouth of the 

 Saskatchewan River. 



If we imagine a specimen of H. catenularia, L., with the corallites 

 brought so close together as to be in actual contact, and to have the 

 meshes so far reduced in size as only to be represented by small, gener- 

 ally triangular, spaces at intervals round the corallites, then we have a 

 typical specimen of H. compacta, Rominger. 



*The word "tube " used by Dr. Rominger, has reference to the corallites, and not to 

 the tubules between the corallites. 



