246 The Ottawa Naturalist. [March 



Original description. — " Corallum composite, apparently 

 forming large depressed hemispherical colonies. Corallites from 

 9 to 15 lines across, the calice slightly concave in the outer half 

 of the width, the central depression three or four lines wide. 

 There are about fifty septo-costal radii in a corallite 14 lines 

 across." " This species differs from Strornbodes pentagomis and 

 Strombodes striatus fboth of which occur in the same beds) in 

 having much coarser radii." 



Additional specimens were collected by J. Townsend on 

 Grand Manitoulin Island in 1883 ; onj specimen in particular 

 shews the structure admirably. 



Further details as to the growth of the corallum are here 

 appended — Corallum composite.'explanatc, discoidal, sometimes 

 over 13 cent, broad and 3 cent, thick, upper surface flat or 

 slightly convex. Corallites upright, confluent, varying in breadth 

 trom 2 to 3 cent., with shallowly concave calyces whose bound- 

 aries are poorly defined and only slightly elevated. Calyces 

 with a well marked, rather deep and comparatively broad 

 central pit, averaging nearly i cent, in width, having steep at 

 times almost vertical sides and a flat bottom. Tabulae, forming 

 a well defined axial area, flat or slightly convex, turned down 

 at their edges, as broad as the pit is wide, about sixteen in a 

 space of 5 mm. Septa, numbering from about forty to fift)-two^ 

 lamellar and uninterrupted in a narrow area surrounding the 

 tabulge, of two orders, the primaries reaching the centre of the 

 tabulae as carinae, the secondaries not infringing on the tabulae ; 

 beyond the confines of the central pit their vertical continuity is 

 interrupted and thcv radiate outward as gradually broadening 

 flatly convex ribs, reaching a maximum breadth of 2 mm. at 

 the edge of the calycinal extension where they meet the septal 

 ribs of adjacent calyces. Pore-openings in the septal ribs have 

 not been recognized in specimens belonging to this species. 

 The vesicular structure supporting the calycinal floors developed 

 at intervals in the upward growth of the colony is composed of 

 blister-hke plates that are rather smaller and less convex than 

 in other species of the genus, also the radially folded calycinal 



