ALECTO. 279 
series, the upper portion of the cells erect, with a circular entire 
aperture.—Johuston. 
1. Atecto GRanuLATA, W. Thompson. 
Hab. On the imner surface of old bivalve shells, more 
rarely on the outer surface. It is a deep-water species. It 
is said to be not uncommon; but the only specimen we 
have met with was on the outer surface of Pinna ingens, 
from the island of Coll. 
It is slender, branched, adherent, the tubular cells lean- 
ing a little to the opposite side. It is glossy, when fresh, 
and dotted with minute granules. When in a dead state, 
it is of a dull white colour. 
2. Atucto mason, D. L. (Plate XVI. fig. 60.) 
Hab. Island of Coll, D. L., from Rev. Mr. Nicol; island 
of Sana, dredged by W. Thompson; Cornwall, Mr. Couch. 
This was a species new to our Fauna when I discovered 
it on a valve of Pinna ingens, from Coll. I sent it to Dr. 
Johnston, and he mentions, in his description of it, that I 
said that the young unbranched specimens resembled a tear 
slowly trickling down the cheek, and swelling in its pro- 
gress. Full-grown specimens, however, are irregularly 
branched, though each branch has the fulness we have 
mentioned, at the termination, It is much stouter and 
