286 MEMORANDA. 
gether; but as, on drying it and subjecting it to the flame of 
a spirit lamp, it becomes more or less distorted, and the 
markings are almost obliterated, I have come to the conclu- 
sion that it is more likely of a membranous nature. 
When the animal, moving through the water, presents the 
edge of its shell to the spectator, this is seen to have scarcely 
any depth, and looks like a cocked hat turned edgeways. 
I have found it in tolerable abundance associated with 
Dijlugia spiralis, D. proteiformis, &c.; but as it is much 
smaller and extremely diaphanous, it may be easily over- 
looked. 
The accompanying drawings of two separate specimens 
found in the same drop of water, though not artistic, are 
faithful representations of the creature and its house, having 
been carefully made under the microscope with the aid of the 
camera lucida. 
If this 7s a new species, I think it may be appropriately 
named “ triangulata.’—Frep. H. Lane, Reading. 
Arachnoidiscus.—In the ‘ Quarterly Journal of Microscopical 
Science’ for April of the present year, pp. 182 and 167, an 
account is given of an Arachnoidiscus found on the Irish 
coast, and it is there stated to be the second occurrence of the 
genus on the British coasts. 
I have in my cabinet a specimen of Odonthalia dentata 
covered with Archnoidiscus, probably Ehrenbergii; it was 
given me in 1857 by Charles Johnson, Esq., Botanical Lecturer 
at Guy’s Hospital, among whose collection of seaweeds it had 
been for about thirty years, and was originally obtained from 
the late James Sowerby, author of ‘English Botany.’ The 
specimen of Odonthalia is British, although the exact locality 
is not stated on the specimen from which the fragment was 
taken.—W. T. Surrotx, Camberwell. 
Maltwood’s Finder.—Your correspondent “A.” very properly 
directs attention to the importance of a uniform method of 
using Maltwood’s finder, and suggests various modes of 
determining the exact position occupied by any object on a 
slide. 
Permit me to place before your readers a description of the 
method which I adopt, and which I find admirably adapted 
to the ready re-discovery of any object, even with the highest 
