162 KAARE MÜNSTER STRØM. 



Subfamily Placodermæ. 

 Genus Penium. Bieb. 1844. 



53. Penium Libellula. (Focke) Nordst. 

 Fairly general, hut scarce. 



54. Penium Navicula. Breb. 

 General, but never in great quantity. 



55. Penium minutissimum. Nordst. 



Very rare. Size: long. 20 ^/, lat. 11,5 f.i. A little greater 

 than the typical form. 



56. Penium truncatum. Breb. 



Rather common. Size: long. 26 .«, lat. 12 /n. 

 hi. Penium margaritaceum.. (Ehrbg.) Breb. 

 Somewhat scarce. Size: long. 77 /ii. 



58. Penium Cylindrus. (Ehrbg.) Breb. 



Common. Many of the specimens observed were quite 

 colour less. 



Size: long. ,«. 36/ 36,2/ 38,7/ 41,2/ 42,5. 

 lat. u. 17/ 16,5/ 16,5/ 16,5/ 16,5. 

 PI. IV, Fig. 13. 



59. Penium exiguum,. W. West. 



Very rare, only two specimens observed, but it is possible 

 that it is overlooked. Size: long. 22,5 f.i, lat. 7,5 f.i. 



60. Penium spirostriolatum. Barker. 



Only in a single sample. Size: long. 240 ji/, lat. 27 ^i. 



61. Penium polymorphutn. Perty. 



Not uncommon. There was a curious, abnormal division 

 in a specimen. Instead of developing two new semicells, the 

 dividing cell developed a spherical, monströse dilatation, just as 

 it has been figured by Borge (Süssw. alg. fl. SpUzberg.) for 

 Penium curtum, and by W. West (Glare Island Survey.) for 

 Euastrum sp. 



62. Penium phymatosporum. Nordst. 

 Rare. 



