279 



Aphyllostylus, sen. nov. 



" Corallum consisting of slender, contiguous, subcylindrical corallites, 

 that are circular or nearly circular in transverse section, and that seem to 

 have formed part of a compound, branched, fasciculate, ascending and 

 somewhat spreading colony, essentially as in Pycnostylus. Surface mar- 

 kings of the exterior of the corallites unknown. 



" The structure of the interior of the, corallites consists of conspicuous 

 transverse tabulae, and of numerous, very minute, spiniform septa. The 

 tabulse, though irregular in their disposition and in their distances apart, 

 are for the most part complete and continuous. The spiniform septa 

 consist of both longitudinal and transverse rows of close-set, very short, 

 straight and inwardly directed, minute spinules, not very unlike those of 

 a Silurian Favosite, but much smaller and shorter. Where the tabulse are 

 comparatively far apart, the longitudinal arrangement of the rows of 

 spinules is very obvious, and there are from four to seven spinules in 

 each longitudinal row, between two of the tabulse. But, in places where 

 the tabulse are close together, the transverse arrangement of the rows of 

 spinules is more apparent, and there are either one or two transverse rows 

 of spinules between two tabulse. 



" The general shape of the corallites in this genus, their mode of growth 

 and their internal tabulse, appear to be essentially similar to those of 

 Pyonostylus, but in the latter the septa are marginal, well developed, and 

 consist of thin, continuous, longitudinal ridges. 



" Pycnostylus i-eems to be most nearly related to Amplexus, Vhich is 

 usually referred to the Zaphrentidse, and it may be that Aphyllostylus 

 should also be included in that family. 



" Aphyllostylus gracilis, sp. nov. 



" Corallites slender, averaging about two or three millimetres in dia- 

 meter ; septal spinules very minute, scarcely visible to the naked eye. 



" This genus and species are based upon fragments of colonies, in six 

 small pieces of limestone of Silurian (Upper Silurian) age, from Stonewall, 

 about thirty-one miles west of East Selkirk, collected by J. B. Tyrrell in 

 1897. Each of these pieces of limestone shows both longitudinal and 

 transverse sections of a few contiguous corallites, upon one or more of its 

 recently broken surfaces. The internal structure of most of these coral- 

 lites is well preserved, but their mode of branching is nowhere very clearly 

 seen. Two or three similar specimens had previously been collected by 

 the writer in 1888 from loose masses of limestone on the banks of the 

 Fairford River, about six or seven miles below the Hudson Bay post at 

 Fairford, Manitoba." 



