no THE SCOTTISH NATURALIST 



of a transparent and colourless chitinoid membrane, passing 

 gradually into a lower ventral (anterior) portion, consisting 

 of a much more delicate, thin, transparent pellicle, very 

 deformable, always exhibiting foldings and wrinklings ; it 

 may be widely open below, and again may completely close 

 the " mouth " of the test by infolding, while sometimes it 

 seems to be partially introverted. Seen from above, the 

 test is circular in outline. The dorsal (posterior) face is 

 margined by two concentric circular ridges, appearing as 

 circles (PI. V., Figs. 1-4); and from its central point, seven 

 (sometimes eight) ridges (lines) radiate towards the margin. 

 Side view shows that the dorsal region or fundus instead of 

 having the form of a rounded dome (as in C.flavd) is much 

 flattened, and only slightly raised towards the centre, gener- 

 ally giving it a low conical form, from the apex of which the 

 seven or eight radial ridges originate. The circular and 

 radial ridges are produced by a slight thickening and eleva- 

 tion of the substance of the test, and may be compared with 

 the rampart of C.penardi and the horns of C. coronata, and 

 their presence naturally adds rigidity to this part of the 

 envelope. They are invariably present, and give a very 

 distinctive appearance even to the empty envelope (PI. V., 



Fig- 3)- 



From the outer and more ventral transverse ridge the 



lateral margins of the envelope descend in a more or less 



regular curve, bulging slightly at first, then narrowing, and 



pass gradually into the ventral wrinkled region. 



No foreign matter occurs on any part of the test. 



The protoplasmic body does not nearly fill the envelope, 

 and no epipodes were observed. In the resting state, it has 

 the form of a rounded or oval mass of greyish protoplasm, 

 containing numerous granules and small food-bodies, and 

 enclosing one or more vacuoles. The nucleus is small and 

 not always conspicuous. Sometimes the body extends and 

 protrudes partially through the aperture of the test as an 

 irregular mass, but no pseudopodia were seen. The inner 

 body of such extended individuals was highly vacuolated. 

 Movement is very sluggish. 



Size. — Small ; varying from 24-30 /ul in diameter, 



