126 Rev. Canon Norman — A Month on 



than in P. concmna — varying in colour from brownish yellow 

 to red, very rarely white ; whole front wall punctate, the 

 pores round the base being larger than the rest. 



The oral opening shows the following variations : — In the 

 voungest state it is semicircular, the lower margin straiglit 

 (Microporellidan) ; then a sirms is developed on the lower 

 margin (and it is Schizoporellidan) ; next a bifid tooth appears 

 within the sinus (it is now ^lucronellidan) ; then the round 

 avicularium is developed in front of the bifid denticle, wliicli 

 last appears to be taken into the wall of the avicularium (and 

 it is now typical Porellidan) ; lastly, a denticle is sometimes, 

 but rarely, developed again within the avicularium and is 

 seen behind it (and the orifice is now typically Smittian). 



Nor are these all the variations, for others occur in the 

 position of the oral avicularium : this sometimes is so deeply 

 seated that it cannot be seen at all from the front, and is only 

 found by looking down into the throat; a large form of the 

 species having the zooecia measuring 1 millim. long instead 

 of 0*6 to 07 millim., which is the usual size, which I have 

 from the St. Lawrence and Greenland, seems always to have 

 the avicularium in this position ; this form may be called var. 

 grcenlanch'ca ; next and typically it is seen just within the 

 oral margin ; lastly, sometimes it is on the margin, which it 

 interrupts. 



The ooecia are very little raised and granulated. Over- 

 growth takes place with certain variations: — (a) A thick 

 crust is developed over the zooecia, in which the punctations 

 are even more conspicuous than in the first cell-wall ; the 

 form of the zooecia is preserved, {h) The zoarium is covered 

 with a similar punctate crust to the last, but here the hollows 

 between the zooecia are filled up, the surface becomes nearly 

 fiat, and on it the zooecia are mapped out by means of narrow 

 raised marginal lines. 



I have a pretty variety from the St. Lawrence ( Whit- 

 eaves). The zoarium is a Ilemescliaran free form ; its 

 surface is nearly flat, the zooecia not being so much raised as 

 usual ; the punctations are all over the surface and con- 

 spicuous, except on a granulated fillet, which, raised above 

 the general surface, completely and evenly encircles the 

 mouth. 



This species may be distinguished from P. concinna by its 

 i)unctate front wall, as well as by its form, colour, OV:c. The 

 latter species always has the general surface of the front wall 

 imperforate and granular, though it has " origelles " (pores) at 

 the base ; the form of the zoojcia is almost invariably shorter, 

 and consequently wider in proportion ; the colour is usually 



