262 MESSES. W. WEST AND G. S. WEST OX 



134. Stalrastrum brachiatum, Kalfs, Brit. Desm. p. 131, t. 23. fig. 9. 



Long. 36-5-55//; lat. 36-5-57o/x; lat. isthm. 9'5-14 /. ; diam. zygosp. cum proc. 

 32-42 y.. 



Several zygospores of this were seen from Orono, Maine. C/r. West, in Journ. Bot. 

 XXV. (1889) p. 205. (PL XVI. fig. 32.) 



135. S. ARcrATUM, Nordst. Bidrag Sydlig. Norges Desm. p. 36, fig. 18. 



Porma ACICTJLIFERA. (PL XVI. fig. 34.) Porma processibus longioribus et horizontaliter 

 dispositis, processibus dorsalibus ad apices leviter dilatatis, spinis ineequalibus, una 

 miilto Ion gi ore. 



Long. c. spin. 27 //, s. spin. 19 // ; lat. (c. spin.) 48-5 /x ; lat. isthm. 9'5 [x. 



The S. arcnatum figm-ed by Wolle (Desm. U.S. pi. 46. figs. 13, 14) is certainly not 

 S. arcuahi/tn, Nordst. 



136. S. SEXVERRUCOSUM, nov. sp. (PL XVI. fig. 35.) S. subparvum, paulo latins quam 

 longius (sine spinis) profnnde constrictum, sinn acnto aperto; semicellulse angnste 

 ellipticcC, angnlis bispinatis serielms tribns granulorum transverse ornatae, dorso 

 verrucis trident iculatis prseditai; a vertice visas triangulares lateribns concavis, 

 angnlis obtusis spinatis, seriebus tribns granulorum transverse dispositis, in ccntro 

 cum annulo verrucaruni tridenticulatarum 6. 



Long. 25 /x ; lat. 34'5 ^ ; lat. isthm. 6 /x. 



The nearest species to this is *S'. arcuatum, Nordst., from which it diff'ers in its thicker 

 and less produced angles, in the dorsal verrucse, &c. 



137. S. VALIDUM, nov. sp. (PL XVI. fig. 36.) S. parvum, IJ-plo latins quam longius, 

 profnnde constrictum, sinn aperto ad extremum subacuto ; semicellulse elliptico- 

 Innatje, marginibus inferioribus leviter biundulatis, apicibns glabris, marginibus 

 snperioribus verrucis emarginatis ornatis, angnlis trident iculatis ; a vertice visae 

 triangulares lateribns concavis et angulos versus leviter undulatis, angnlis productis 

 truncatis et tridenticulatis, intra marginem lateralem unumquemque verrucis 

 emarginatis 4 ornatse, verrucis duabus prope apicem anguli uniuscuj usque ; in 

 centro glabrae. 



Long. 27-29 /x; lat. 36-38 /x; lat. isthm. 7-7-5 /x. 



138. S. DELiCATissiMUM, nov. sp. (PL XVI. fig. 37.) *S'. parvum, paulo longius quam 

 latins, modice constrictum ; semicellulae obtriangulares, lateribns snperioribus 

 minutissirae biundulatis, apicibns subrectis, angnlis processibus delicatissimis longis 

 glabris productis, apicibns leviter dilatatis et subtruncatis ; a vertice visse triangulares, 

 lateribns subrectis, spinis minutissimis duabus instructis, angnlis in processus 

 uehcatissimos glabros productis. 

 Long. s. proc. 115 /x, c. proc. 34 /x; lat. s. proc. 9-5 ^, c. proc. 30 /x; lat. isthm. 4 /.. 

 The minute spines on each side of the vertical view show best when the plant is seen 

 obliquely. 



