50 DUBLIN NATURAIi HISTORY SOCIETY. 



segments in front view. It perhaps most approaches C. margmitiferum 

 (Menegh.), but, besides its smaller size, it differs from that species aiid 

 C. latum (Breb.) in not having reniform or semi-orbicular segments, as 

 well as in the constriction being not a linear, but a wide notch. The 

 same characters distinguish it from C. BreUssonii (Menegh.), as well 

 as the pearly granules being minute and closely scattered, not rather 

 widely distributed and conic. From C. tetraopUhalmum (Breb.) it also 

 differs in the same characters, as well as in that of the superficial gra- 

 nules, which in that species are broad, giving the margin a somewhat 

 undulate or crenate, rather than a minutely denticulate appearance. 

 Prom C. Broomei (Thwaites) and C. hiretmi (Breb.), it differs, besides 

 other characters, in its elliptic, not quadrilateral or angular segments. 

 From C. prmmorsum (Breb.), G. notahile (Breb.), and C. JBotnjtis (Me- 

 negh.), as well as C. protracttmi (IS'ag.), C. gemmiferum (Breb.), and C. 

 Turpinii (Breb.), it differs in having roanded, not truncate ends, and 

 from all the species just named in the central constriction, not forming 

 a linear, but a wide notch. 



It is at once distinguished from C. orUculatum (Ealfs), with which 

 it agrees in the constriction not forming a linear notch, by the segments 

 being elliptic, not spherical, and the end view not circular ; besides the 

 pearly granules being minute and depressed, not elevated and conic. It 

 is true that Professor de Bary (" Untersuchungen liber die familie der 

 Conjugaten," PL VI. 49 a h), alludes to a Cosmarium called by him 

 Cosmarium orhiculatimi (Ralfs), which, I apprehend, is actually the 

 species now described, but, with great deference, I think he is wrong ; 

 this form differs quite from C. orbiculatum (Ealfs), as much, indeed, as 

 C. hioculatim (Breb.) does from G. moniliforme (Ealfs). Assuming 

 that I am right in the conjecture that the present species is identical 

 with that alluded to by De Bary under the name of G. orUculatum 

 (Ealfs), the sporangium has been provisionally described in the fore- 

 going specific characters, taken from the figure given by that observer, 

 although I have not myself met it conjugated. 



As to other granulate species, so far as I am aware, it needs only 

 to contrast this form with C. pluviale (Breb.), with which it agrees in 

 being compressed, and in the constriction not forming a linear notch, 

 but it differs in the form of the segments, which, in the species just 

 named, are nearly as broad as long, sub-ovate or sub- orbicular, ends 

 rotundato-truncate ; whereas, in the species in question, the segments 

 are broader than long, elliptic, and ends rounded, the constriction form- 

 ing a short neck. Of the smooth species, it most nearly approaches G. 

 Uoculatum (Breb.) in form, but the granulate surface of the present 

 species at once distinguishes it. The same circumstance, as well as the 

 want of the solitary superficial projection on each front surface of the. 

 segments, separate it from C.pJuiseolus (Breb). 



I am not aware of any other species with which it seems at all re- 

 quisite to compare the present form, nor does there indeed ai)pear to me 

 any danger, with proper attention, of confounding it with any of those 

 I have mentioned. This has occurred to me for three or four succes- 



