PROCEEDINGS OF SOCIETIES. 137 
less deep constriction, and angles not inflated in the end 
view ; from Staurastrum cuspidatum (Bréb.), the end view of 
which the triangular variety most approaches, by its much 
smaller size, straight sides in end view, and non-inflated 
angles, and by the want of a connecting band in the front 
view. It resembles more nearly Staurastrum minus (Kiitz.), 
an end view of which is figured in Ralfs’ Monograph, but 
which has not yet (I believe) been found in Britain; but that 
species presents five angles, not three or four, as in this 
species. Ido not think I need contrast it with any other 
species. The angles in the end view of the quadrangular form 
are right angles, and the sides straight; in the triangular 
form the end view is equilateral and straight-sided, both forms 
possessing a single awn or acute spine at each angle. The 
awns are a little longer in the triangular variety than those of 
the quadrangular. I was fortunate enough to meet with the 
Sporangium of this species; it is spherical and acutely 
spinous; in fact, very like that of <Arthrodesmus incus. 
That this form is a sort of connecting link, as it were, be- 
tween Arthrodesmus and Staurastrum seems probable, from 
the remote likeness in the front view to Arth. incus, as well 
as from the similarity of the sporangium in each. I would, 
therefore, venture to put forward the following to serve as a 
description of this species : 
Staurastrum O’ Meari, n. sp. 
Frond very minute; segments smooth, ends truncate (in 
the quadrangular variety slightly convex) ; central constric- 
tion not deep, forming an obtuse angle; constricted portion 
very short; a single awn at each angle; awns diverging in the 
front view, acute. 
End view quadrangular or triangular; sides straight ; angles 
not inflated. 
Sporangium orbicular, spinous; spines at first subulate, 
afterwards slightly inflated at the base, acute. 
Length of frond of quadrangular ata SEE6 
br eadth at end (exclusive of Soe zso03 
isthmus, 37'+5; length of spine, s¢'o0- 
Length of frond of triangular variety, 755th of an inch; 
breadth au end (exclusive of ey, aza07; diameter at 
isthmus, 52455; length of spme, 3755: 
Diameter of sporangium, vee including spines, 7759 of 
an inch; including spines, 37th of an inch. 
It is with very great pleasure I am permitted to call this 
species after my friend, the Rey. Eugene O’ Meara, to whom I 
of an inch; 
diameter i 
