116 CONTRIBUTIONS TO CANADIAN PALAEONTOLOGY. 



Zaprhentis genitiva, Billings. 1874. Canadian Naturalist, new series, vol. VII., p. 235. 

 Hcterophrentis prolifica, Billings. 1874. Ibid., p. 236. 



Zaphrentis prolifica, Rominger. 1876. Geol. Surv. Mich., Foss. Corals, p. 146, pi. 

 LIII, upper row. 



Corallum simple, conical, slightly curved, pointed and sometimes rather 

 attenuated at the base, often annulated by well marked rounded growth 

 ridges. Epitheca complete, showing fins transverse growth lines and longi- 

 tudinal septal furrows. Corallum attaining a length of as much as 1 65 mm., 

 measured on the convex curve, with a breadth at the cup rim of about 60 

 mm., but with an average size in small specimens of between 50 and 

 70 mm. in length by from 25 to 35 mm., in diameter above, with all 

 gradations between these extreme sizes. Calyx with steep walls, its 

 depth often nearly equal to about one-half the height of the corallum : 

 in large specimens not quite so deep. Septa well developed, of two sizes 

 alternating, some of the primaries generally extending to the centre 

 where they are twisted, the secondaries equal in length to about one-sixth 

 the diameter of the corallum ; in large specimens numbering in all up to 

 about one hundred and thirty or even more, in small specimens from 

 ninety to one hundred. Dissepiments occupying the interseptal loculi,. 

 large, arching from the walls upward and inward toward the centre 

 where they are more or less horizontal and often contorted and twisted. 

 The inner ends of the primary septa appear in the broadly convex cup 

 bottom as sharp-edged converging keels that either combine at the centre 

 to form a more or less exsert laterally compressed boss or become twisted 

 together without the formation of a decided central prominence or as is 

 not infrequently the case the centre may be smooth and comparatively 

 free of septa. The primary septa often coalesce in twos and threes near 

 their inner ends. A deep lateral septal fossette is present in the bottom 

 of the calyx and extends toward the centre in line with the longer axis 

 of the central projection ; its position is independent of the curvature of 

 the corallum. In the calyx the septa gradually change into low, rounded 

 ridges as the rim is approached. 



Localities and formations. — Abundant in the Corniferous limestone of 

 Ontario ; collected by E. Billings in 1857 at Rama's Farm, Port Col borne, 

 and by E. and J. DeCew in the township of Cayuga in the same year : 

 there are also specimens in the collection from the Corniferous of the 

 townships of Oneida and Walpole. Not uncommon in the Hamilton 

 formation of Ontario. Also from rocks of Devonian age at Long Portage, 

 JV1 issinaibi River to Moose Factory, R. Bell, 1877, as well as some loose 

 specimens collected by Mr. George Barnston on the Moose River. 



The specimen described as Zaphrentis corticata, is from Split Rock, 

 Perce, Que., collected by T. Curry : Lower Devonian (Billings). 



