1S90.] MICKOSCOPICAL JOURNAL. UY 



or this beautiful species, two f'ornis were noticed alon<^ with the type. 

 One, a nine-rayetl I'orm, was seen several times; the other, a very long 

 and slender-armed one, mcasuretl 145 // across the arms. Cooke and 

 Wolle describe the end view as 7 (nirely 6 or 8) rayed ; tlie forms from 

 Capel Curig are almost all S-rayed. 



Fig. 16. — Staurastruin cyrtoccrtiin Brt-b., foima tctragona. (Forma 

 a vertice tetragona.) 



Fig. 17. — Docidiuvi elongatiini nov. sp. (D. quadragies longius 

 quam latum, ad utrumque polum sensim attenuatum, apicibus trunca- 

 tis, medio non inflato.) 



Frond about forty times as long as broad, the straight sides gradually 

 tapering from the uninflated base of each semicell to the truncate apex. 



Fig. iS. — Cosi}iarii(in orbicidatum Ralfs. The figure is given 

 merely for comparison with Fig. 19. 



Fig. 19. — Cosmariiini isthmiuin nov. sp. 



This form is the same as C. cxcavatiiin Nord, var. ditplo-tnajor 

 Lund., as described and figured by Wolle. As the author does not be- 

 lieve this species to be a variety of C. excavaium, he proposes the above 

 name. A. W. Bennett, however, does not adopt the name, but believes 

 the form identical with C. orbiculatum^ the width of the isthmus being 

 merely an indication of early stage of division. 



Fig. 20. — Staiirastrtitn spinifertun nov. sp. (S. parvum, scmi- 

 cellulis ellipticis cum octo spinis (circa) ad margincm semicelluhe sin- 

 gulis, a vertice triangulare cum s^jinis novem, lateribus leviter conca- 

 vis.) 



Segments elliptic, with al)out eight spines in tlie periphery of each 

 segment; end view triangular, sides very slightly concave, showing 

 two spines between each apical one. 



Fig. 21. — XantJiidiiini cristatuvi Breb. var. spiiiuliferiiiii nov. 

 var. (Var. cum quattuor vel cjuinque spinis parvioribus additis ina^- 

 qualiter ordinatis intra marginem semicellulae singular.) 



This has four or five additional spines, rather unequally disposed 

 just within the margin of the front view of each semicell. 



Fig. 22. — Staurastrum controversiim Breb. The figure is given in 

 order to show a variety of this variable species. 



Fig. 23. — Clostcrmtn striolatum Eh rb., forma recta. (Xon cur- 

 vata, rectissima.) 



This dirt'ers from the type in having no curvature ; several examples 

 were seen, and were turned over and over. 



Fig. 24. — Pc?iiH)u spirostriolatuDi Bark. As this species appears 

 to vary in difi'erent localities, some figures are given. This variabilitv 

 has been noticed from Maine, N. Ireland, .Scandale in the lake district, 

 and Glen Shee and Craig and Lochan in Scotland. The parallel 

 striae can often be seen on both the upper and under surfaces of the 

 empty cylindrical frond, and then they appear as if they crossed each 

 other. 



Fig. 25. — Cos7nariiim tctraopht/ialnmni var. suhrotuiidu7}i nov. var. 

 Newborough Warren. (Var. sinu apertissimo semicellulis subrotundis 

 facto.) 



This dilVers from the type in the open sinus caused by the subrotund 

 semicells. 



Fig. 26. — ]£iiastruni vcrrucosiiiii Ehrb. This is a variety with more 

 gaping sinus thrm usual and a subrectangular polar lobe. 



