386 Transactions of the Society. 



at the point of junction. This opening, however, appears to be 

 merely accidental and is not present in the majority of specimens. 

 The cement used is not ferruginous, but appears to consist of very 

 fine homogeneous mud. It is absorbent and very easily broken up, 

 and is no doubt very porous, thus serving for the passage of the 

 protoplasmic extensions. 



As with Psammosphivra rustica, it is not easy to give a verbal de- 

 scription of this species, because owing to the nature of the material 

 hardly any two specimens are exactly alike. As will be seen from 

 the figures the mode of construction is apparently to select a number 

 of small flakes of mica (an abundant constituent in most North Sea 

 dredgingsj. These are arranged so as to make as nearly as possible 

 an oval or flask-shaped enclosure, and the gaps between the edges of 

 the plates are then filled up with a thin framing of mud-like cement. 

 Owing to the irregular shape and size of the mica flakes the amount 

 of cement used in different parts of the test varies from a narrow 

 strip joining two parallel edges of mica, like the putty round a 

 square of glass in a window, to a broad flat layer stretching across 

 a gap between two adjacent mica plates. In the latter case the 

 edges of the mica plates usually project slightly from the edges of 

 the test, forming salient angles, the cement being attached to the 

 inner edge of the flake. There is no attempt to fill in such cavities 

 by the selection of a suitably small flake of mica, in the neat manner 

 in which Psammosphcvra rustica matches its constituent spicules 

 to the space required to be filled. 



The final result attained by the worker is the construction of 

 an irregularly oval flask with from four to eight flattened "windows " 

 in the sides. 



The protoplasm is very dark and opaque, and fills about one 

 half of the internal cavity. 



The specimens vary considerably in shape and size, but the 

 most usual form has a length about twice its breadth. Average 

 length 0-4-0 -6 mm., breadth 0-25-0 -35 mm. 



Psammosphxra Bowmanni occurs only in a single area so far as 

 our observations go. It is confined to the deep water in the 

 bottom of the gully off Burghead, in the Moray Firth. (' Gold- 

 seeker ' : Haul 73, Burghead, S. ^ W., 3 miles, 35 fathoms ; and 

 Haul 7791, Burghead, S. by E., 2 miles, 55 metres.) The material 

 consisted of a black mud with abundant Foraminifera, including 

 many rare and interesting types, such as Botellina lahyrinthica 

 (Brady) and Hippocrepina indivisa (Parker). Specimens are fairly 

 frequent in this gully, but owing to the fragile nature of the 

 cement the majority are broken in the process of cleaning the 

 material. 



Mica is a somewhat favourite building material with a few 

 Foraminifera, which show selective tendencies. RcopJiax Scottii 

 (Chaster) builds its elegant, many-chambered shell entirely of 



