156 CONTRIBUTIONS TO CANADIAN PALAEONTOLOGY. 



ruptly expanded at corresponding levels, the expansions, generally concave- 

 ly curved below and flat above, meeting in polygonal outlines and forming 

 a succession of continuous level floors one above the other, representing 

 a repetition of calicular extensions, between which the cylindrical unex- 

 panded parts are separated from each other by spaces generally less in 

 width than, although sometimes equal to or exceeding, the half diameters 

 of the cylindrical parts. The distance apart of the horizontal floors is 

 moderately constant in the same individual, but variable in different 

 specimens ; in one specimen as many as sixteen occur in a space of 

 5 cent., in another only three or four are observed in the same distance, 

 the average number- being eight or ten in 5 cent. Average breadth of 

 cylindrical parts of corallites about 9 mm., that of the expansions about 12 

 mm., the difference, however, between the unexpanded and the expanded 

 parts is often much greater in some specimens, the latter reaching a breadth 

 at times of over 2 - 5 cent, with a breadth in the former of about 10 mm. 

 The whole of the exposed surface of the corallites is covered by a strong 

 epitheca marked by fine annular sculpture lines, about 12 in a space of 

 2 mm., as well as by occasional slight but distinct growth swellings or 

 constrictions and longitudinal, narrow septal furrows. The thin edges of 

 the expansions of adjacent corallites not entirely coalescent but separated 

 from each other by a thin wall which is evidently the upward extension of 

 the epitheca. Calyces circular, rather shallow with horizontally expand- 

 ed margins slightly raised above the surrounding floor, flat at the bottom 

 where the inner wall with its enclosed upper tabulum appears. Septa 

 from about fifty to sixty in number, of two alternating sizes, the longer 

 not passing to the centre of the visceral chamber but by the union of 

 their inner edges forming a wall that encloses the central tubular area, 3 

 or 4 mm. in width, holding horizontal tabulae of which there are nine or 

 ten in a space of 5 mm. ; the shorter septa fall short of the inner wall. 

 The septa extend outward through the expansions but are not conflu- 

 ent with those of contiguous corallites ; throughout they are decorated 

 on their side faces by close-set, obliquely and inwardly ascending carinse, 

 from about six to ten in the space of 2 mm., that appear on their free 

 edges in the cup as minute transverse bars or denticulations. Small dis- 

 sepiments curving convexly upward and outward occupy the interseptal 

 spaces between the inner ends of the secondary septa and the outer wall. 

 Pore-like openings, similar to those observed in the different species of 

 Phillipsastrtea, are here also found in the dissepiments. Increase by lateral 

 calicular gemmation, the buds appearing as if springing from the floor be- 

 tween the corallites. 



Locality arid formation. — Abundant in the Corniferous limestone of 

 Ontario. 



