22 CONTRIBUTIONS TO CANADIAN PALAEONTOLOGY. 



responding increase in breadth. The corallites are compressed and 

 diverge from one or more basal points outward with calyces oblique to 

 the upper surface ; they are thin walled throughout their length and vary 

 in breadth from -5 to 1 mm., with a height of about -25 mm. Pores of 

 moderate size placed at the angular edges of the corallites. Tabulae 

 numerous, directly transverse, about -5 mm. apart. In some of the Lake 

 Huron specimens a longitudinal ridge is present on the lower side of the 

 calyces, and two or three rows of septal spines can be seen projecting from 

 the inner surface of the upper wall of the corallites. 



Of this species Milne-Edwards and Haime remark that it very closely 

 resembles A. suborbicularis, Lamarck, of the Devonianformation, a species 

 that has not as yet been recognized in Canada. 



Alveolites Niagarensis,* Rominger. 



Alveolites Niagarensia, Rominger. 1876. Geol. Sur. Mich., Foss. Corals, p. 39, pi. 

 XVI., figs. 1 and 2, but not A. Niagarensis, Nicholson, 1875. 



" Convex hemispherical masses of concentrically laminated structure, 

 covered by an epithecal crust on the lower concave side, or 

 undose, discoid expansions composed of superimposed layers of 

 prostrate tubes, diverging with a slight spiral twist from a central 

 vertex, several of which are sometimes observed on an expansion. The 

 compressed tubes are always more convex on the upper sides, with a corres- 

 ponding concavity of the lower sides, which rest on the convexities of the 

 subjacent tubes. The compression is sometimes only moderate, and the 

 outside of the oblique orifices is formed by a projecting arched lip ; in other 

 specimens the compression is stronger, the orifices become narrow, lanceo- 

 late, or fissure-like, with an appressed subplane lip on the outer side. The 

 orifices of the majority of specimens are surrounded by a cycle of denticules, 

 corresponding to longitudinal rows of spinules along the inner surface of 

 the tube walls. The rows are rarely fully twelve in number, and some of 

 them are always more strongly developed than others. In some specimens 

 no denticulation of the orifices can be observed, and the tube channels are 

 found to be almost smooth ; this is not the case in all cases owing to the 

 want of development of the crests or spinules ; these seem often to have 

 been obliterated by imperfect preservation in the process of petrification." 



* In 1889 Mr. S. A. Miller in his "North American Geology and Palaeontology" 

 proposed the name A. wndosua for this species. As Nicholson had already, in 1875, in the 

 " Palaeontology of Ontario " described a dendroid coral from the Niagara limestone at 

 Rockwood, Ont., under the name Alveolites Niagarensis, and as this coral is not aa 

 Alveolites but most probably a Cladopora, the specific name of Rominger's coral is here 

 retained. 



