Silurian ond Devonian Fossils of Canada, 429 



cupying the place of one of the radiating septa ; these are in 

 general well developed, denticulated upon their margins, and 

 extend upon the surface of the transverse diaphragms to the cen- 

 tral of the visceral chambers. 



Edwards and Haime in the Polypiers Fossiles, page 326, have 

 in substance given the above definition of this genus. In some 

 of the species there is a rudimentary columella, and sometimes 

 even in the same species the radiating septa may or may not 

 reach the centre in different individuals. 



Zaphrentis prolifica (Billings). 



Description. — Corallum simple, turbinate, curved, with a few 

 broad shallow encircling folds. Septal fossette of a pyriform 

 shape, gradually enlarging from the margin towards, but not quite 

 reaching the centre, variable in its position in relation to the 

 curvature of the fossil. Radiating septa in the adult specimens 

 between sixty and seventy-five of the larger size, alternating with 

 a lihe number of smaller ones, the former in some of the individuals 

 extending to the centre on the bottom of the cup, where they are 

 spirally twisted or irregularly contorted, in other specimens not 

 reaching the centre,, which is then occupied by a smooth space or 

 often with a columella elongated in a direction from the septal 

 fossette towards the opposite side. The septa are also sharp- 

 edged for about half the distance from the bottom of the cup to 

 the margin, then become gradually less projecting until at the edge 

 of the cup they are reduced to mere flat rounded ridges. Length 

 from four to five inches or a little more. Width of cup from two 

 inches to two inches and a-half. Depth of cup about one inch. 



Very numerous specimens of young individuals of this species 

 one inch and a-half and upwards in length, and with fifty 7 or more 

 principal radiating septa occur along with those full grown. These 

 Email ones might perhaps be regarded as constituting distinct 

 species, but when good specimens can be observed they all exhi- 

 bit the characters which are persistent in the large individuals. 



The presence of the columella seems at first sight to be a suffi- 

 cient ground for placing the individuals in which it occurs in the 

 genus Lophophyllum (Edwards and Haime). I have however 

 examined a great number of specimens and have found every 

 gradation between the following characteristics. 



1st Specimens with a perfectly smooth space in the bottom of 

 the cup, no columella. 



