132 CONTRIBUTIONS TO CANADIAN PALAEONTOLOGY. 



distance from the inner surface of the outer wall, but the tabulae, though 

 well developed and complete, are entirely horizontal and neither bend 

 upwards at the periphery nor embrace each other with their reflexed 

 margins. Corallum compound, consisting apparently of an aggregation 

 of numerous, slender, cylindrical or sub-cylindrical polyp stems, which 

 divide by calicular gemmation at distant intervals into sets of three, four 

 or more, ascending, sub-parallel, contiguous, i\ kuous branches. Structure 

 of the calices previous to gemmation, and ch.iracters of the basal portion 

 of the corallum unknown." ( Whiteaves.) 



Type species. — P. Guelphensis, Whiteaves. 



Dr. Whiteaves (Pateoz. Foss., vol. III., pt. II., p. 49, 1895), further 

 remarks : " The genus Pycnoslylus, of which Orthoposdium, Schluter, 

 1889, is probably a synonym, differs from Amplexus only in the circum- 

 stance that it grows in colonies of compound and apparently fasciculated 

 corallites." 



PrcNOSTYLUs Guelphensis, Whiteaves. 



Plate X., figs. 4, 4a. 



? Amplexus laxatus, Billings, IStJS, Geology of Canada, pp. 340 and 342, -with no 



description nor figures. 

 Amplexus (?) sp. Nicholson, 1875. Palseon of Ont., p. 66, 



Pycnoslylus Guelphensis, Whiteaves, 1884 Palseoz. Foss., vol. III., pt. I., p. 3, pi. 

 I., figs. 1, la, 16. 

 Whiteaves, 1895. Ibid, pt. II., p. 49. 



Original description. — " Corallites long and slender, averaging from 

 3 to 7 mm. in diameter, and dividing uniformly at the same point 

 into either three or four branches. Epitheca marked by transverse 

 constrictions and re-elevations at irregular distances, but not longitud- 

 inally ribbed. Primary septa alternating with smaller secondary ones." 



Localities and formation. — New Hope (name changed to Hespeler in 

 1858), Ont., E. Billings, 1857 ; Guelph, Ont., R. Bell, 1861 ; Hespeler, 

 Ont., T. C. Weston, 1867; Elora, Ont., Mr. D.Boyle, 1880; Durham, 

 Ont., Mr. J. Townsend. Guelph limestone. 



It may also be remarked that — the septa average thirty-two in 

 number, the primaries being about -75 mm. in length when well pre- 

 served, the secondaries slightly smaller. The tabulae are complete, 

 flat, often slightly convex or concave, rather far apart, from five to 

 nine occurring in a distance of 1 cent. The corallites often touch each 

 other and sometimes continue • in contact for some distance, and are 

 seldom more than their own diameters apart. In longitudinal sections 

 the new corallites, in sets of four or occasionally three, are seen to 

 spring simultaneously from the inner surface of the wall of the parent 



