280 MYRIOZOID^. 



endency to radiation^ the marginal punctures are a 

 conspicuous feature^ and the peristome is greatly deve- 

 loped, especially in the fertile cells, in which it forms a 

 wall round the orifice. There is no trace, however, of the 

 broad and prominent umbo with a cup-like cavity above 

 it, which, according to Busk, distinguishes the Crag repre- 

 sentatives of the species. This second form has occurred 

 on the coasts of Antrim and Cornwall^. 



The first of these varieties seems to agree very closely 

 with the Flustra Dutertrei of Audouin. The Crag form 

 agrees generally with the Antrim and Cornish specimens; 

 and with these may be ranked the Tertiary Lepralia aurita 

 of Reuss. 



I see no sufficient reason for separating these varieties 

 specifically, though they certainly present a very different 

 appearance; and I have therefore restored Audouin's 

 name. A Madeiran form, mentioned by Busk, seems to 

 combine some of the peculiarities of eachf; and I have a 

 specimen from Antrim in which there is a curious blending 

 of the characters of the two varieties. It has the elevated 

 peristome in the fertile cells and the flat surface which dis- 

 tinguish the form /3; but there is a decided tendency 

 towards the radiate arrangement of the granules, whilst in 

 one half of the colony the marginal punctures are a con- 

 spicuous feature, and in the other are altogether wanting. 



The Hippothoa pes-anseris of Smitt, from the Gulf of 

 Florida, seems to differ from the present species in a single 

 character only — the remarkable shape of the vibraculum, 

 which curiously imitates the webbed foot of a bird. 



Habitat. On shells and stone, from deep water. 



* The specimens from these localities stand alone in having the peri- 

 stome elevated into a wall round the mouth in front of the ooeeium. The 

 cells are also somewhat more depressed than in the Shetland variety. 



t Quart. Journ. Microsc. Sc. viii. p. 284. 



