DUBLIN NATURAL HISTOET SOCIETY. 49 



out that the Limerick specimens were not identical either with the Kil- 

 lamey form of the plant or the Glonincaragh plants, but were interme- 

 diate between the two. 



]\Ir. r. J. Foot had seen the Trichomanes growing in its new station. 

 He took this opportunity of adding, to his Clare list of ferns, Asplenium 

 acutum, which he had met since the publication of his list. 



Professor Kinahan submitted a notice of some rare animals which 

 had occurred to him during his researches. The more remarkable were : 

 Ophidium imlerle — Dalkey Sound ; new to Ireland, Templeton's notice 

 having reference to a distinct animal. Crihella rosea — Dublin Bay. 

 Galatliea dispersa ; south of Dalkey Island. Pagurus Prideauxii — dredged 

 at the back of Dalkey Island, in company with Adamsia palliata. Pagu- 

 rm Icevis, Shanganagh. Crangon lispinosus, Killiney Bay. Specimens 

 of the several species were exhibited. 



The following paper was then submitted : — 



DESCEIPTION OF A NEW SPECIES OF COSMAEIUM, AND OF A NEW SPECIES OF 

 XANTHIDIUM. BY W. AKCHER. 



Plate I. 

 Family.— DESMIDIACE^. 



Genus. — Cosmaeium ( Corda). 

 Cosmarium Portianum {sp. nov.). 



Specific characters : Frond deeply constricted ; segments, in front 

 view, broadly elliptic, rough with minute, scattered, pearly granules, 

 constriction deep, wide, isthmus forming a short neck ; end-view elliptic. 



LocaUty : Pools, Dublin and Wicklow Mountains ; not uncommon. 



Greneral Description : Frond minute, compressed, in front view about 

 one-third longer than broad, rough all over with minute, scattered, some- 

 what depressed pearly granules, which give a minutely denticulate ap- 

 pearance to the margin, deeply constricted at the middle, the constriction 

 forming a gradually widening notch at each side, rounded below ; seg- 

 ments, in front view, broadly elliptic, in side view, suborbicular, con- 

 nected by a rather narrow isthmus, forming a short neck ; end view, 

 broadly elliptic. (Sporangium, after a figure by Professor De Bary of 

 an undescribed species supposed to be the present : orbicular, beset with 

 somewhat elongate, conical, blunt spines.) 



Measurements : Length of frond, ^^q ; breadth of frond, g|^ of an 

 inch. 



Plate I. — Fig. 8, front view ; Fig. 9, end view. 



Affinities : The granulated surface and compressed frond in this 

 species forbid its being mistaken for any of those in which the surface 

 is smooth, or the end view circular. Of those species with which it 

 agrees in the characters first indicated, it is about the most minute, and 

 I believe it is otherwise amply distinguished from them by its elliptic 



H 



