ALGJ3 OF WEST IRELAND. 167 



tt8. Xanthidium apiculifeiuim, nov. sp. (PL XXIV. fig. 17.) 

 X. pusillum, tarn Ion gum quam latum, medio modice con- 

 strictum, sinu angusto extrorsum dilatato ; semicellulaB trape- 

 zoido-pyramidatae, apicibus late truncatis spinas binas breves 

 medium gerentibus, angulis inferioribus subrotuudatis spinam 

 unam brevem gerentibus, angulis superioribus spinas biuas 

 breves gerentibus ; a vertice visae ellipticae brevi spina ad unum- 

 quemque polum, medio utroque latere tumore pusillo ; a latere 

 visse subcirculares. 



Long, cum spin. 12-5 \x, ; long, sine spin. 11'5 ft ; lat. cum 

 spin. 12*5 /i ; lat. sine spin. 12 p; lat. isthm. 5 /x ; crass. 6*5 /x. 

 I. Lakes near Recess. 



9. X. coircnrertrif, Arch., ttvar. Boldtiana, nov. var. [Ar- 



tbrodesmus hexagonus, Boldt, forma, Boldt (Siber. Chloroph. 

 taf. 5. fig. 17).] (PI. XXII. fig. 6.) 



Boldt's figure of A. hexagonus (I. c. fig. 16) seems to agree 

 exactly with the description of X. concinnum, Arch. (Journ. 



Micr 



Boldt also has a form of 



his above-mentioned species (fig. 17) ; this form appears to be 

 the same as the Irish plant, so I propose to name it after Boldt 

 as a variety of Archer's species. This belongs to the genus 

 Xanthidium, because the semicells have a distinct central pro- 

 tuberance. 



L Near Oughterard ; Moher Lough. — II. Lower Lake of 

 Killarney, near O'Sullivan's Cascade. 



Specimens from Moher Lough : 



Long. 14 xx ; lat. sine mucr. 12-5 /x ; lat. cum mucr. 1G tx 



lat. isthm. 4 xx ; crass. 8 xx. 



Specimens from near Oughterard: 



Long. 10 n ; lat. sine mucr. 10-11*5 p; lat. cum mucr. 12*5- 

 14 xx ; lat. isthm. 4-5 xx ; crass. 65 //. 



1. Arthrodesmus octocobxis, Ehrerib. (Xanthidium? octo- 

 corne, Ralfs, Brit. Desm. p. 116, tab. 20. fig. 2.) 



Long. 18-21 xx; lat. sine spin. 15-16 xx; lat. cum spin. 28- 

 30 xx; lat. isthm. 5-6/i. 



I. Ballynahinch ; Koundstone ; Lakes near Recess ; Baheh 

 Loughs ; Lough Shannacloontippen ; near Oughterard ; Lough 

 Aunierin; Creggan and Derryclare Loughs; Glendalough ; 

 Letereen Lough. — II. Cromagloun ; Lough Guitane ; Muckross ; 



Linr. JOUEN. — BOTANY, YOL. XXIX. O 



