240 MESSES. W. WEST AND G. S. WEST ON 



Var. TUMiDA, nov. var. (PI. XIV. fig. 7.) Var. semicellulis tumore basali utrobique 

 ad medium ; a basi visis processibus lateral ibus brevioribus et submcurvatis ; 

 isthmo circiilari. 

 Long. 195 m; lat. 122 ju; crass. 87"5-40(M.; lat. isthm. 16*5 ju. 



This variety differs from the typical form in having a central protuberance near the 

 base of each semicell. This is most readily seen from the basal view of a semicell or 

 from the lateral view. The isthmus is also circular and not elliptic. 



42. MiCRASTERiAS APTCULATA, Menegh. in Linnaea, xiv. (1810) p. 216 ; Cooke, Brit. 



Desm. p. 186, pi. 48. fig. 1 [after W. B. Turner]. {Euastimm apieulatum, Ehrenb. 

 Infus. p. 167, t. 12. fig. 2.) (PL XIV. fig. 12.) 

 Long. 228 |M.; lat. 226 /x; lat. isthm. 30 yu. Lat. : long. = l : 1*004. 

 „ 254^; „ 226 At; „ „ 35 1.. „ „ =1:1-124. 

 „ 294 m; „ 250 60; „ „ 36 m. „ „ =1:1-176. 

 As the figure of this species given by Wolle (Alg. U.S. pi. 56. tig. 3) is so widely 

 different from any forms with which we are acquainted, we give a figure of the American 

 form we meet with, which differs from the European form only in being rather wider ; 

 we propose that tiie form figured by Wolle be named var. Wollei. 



Subsp. FiMBRiATA, Nordst., var. spinosa, Biss. (Boy et Biss. in Ann. Scot. Nat. Hist. 



(1893) p. 173, pi. 1. fig. 3). 

 This seems to be one of a series of forms connecting M. apiculata with M, fimhriata. 



43. M. EADiosA, Balfs, Brit. Desm. p. 72, t. 8. fig. 8. 



Var. ORNATA, Xordst. in Vidensk. Meddel. 1869 (1870), p. 223, t. 2. fig. 11. 

 Long. 112 ju ; lat. 110 ^ ; lat. isthm. 16 ^. 

 llah. Minneapolis, Minnesota. 



Var. SwAiNii, nobis. {3Bcrasterias Swainii, Hastings, in Wolle, Desm. U.S., new edit, 

 p. 119, pi. 42. fig. 1.) 



We consider that M. Swainli, Hastings, is but a variety of this very variable species. 

 We give a figure (PI. XIII. fig. 30) of a form (long. 150 /i, lat. 151 /u, lat. isthm. 11-5 u) 

 sufficiently near his to show this, although the polar lobe of this example is abnormally 

 narrow compared with other American specimens ; the latter generally possess a broader 

 polar lobe than British examples. 



44. M. sPECiosA, Wolle, Alg. U.S. p. 38, pi. 56. figs. 1, 2. 



The typical form of this has the short peripheral spines set on like those of 31. apicu- 

 lata, Menegh., as one would infer from WoUe's description, though his fio-ure does not 

 show this. 



Long. 144-153 ix ; lat. 132-135 /u ; lat. isthm. 16-21 ^. 



Pormalaciniisperiphericis mucronatis (non spiniferis); membrana granulato-punctata. 

 Long. 150-154 m ; lat. 125-132 fi ; lat. isthm. 15-22 ^. (PI. XIV. tigs. 10, 11.) 

 This form, so far as we have observed, always has the ultimate divisions of the lateral 

 lobes subacute and submamillate ; this also applies to the 6 "mucros " of the polar lobe in 



