Desmidsfrom Massachusetts, U.S.A. By Wm. West. 17 



P. margaritaeeum Breb. Frequent. 



P. polymorphum Perty. 



P. Brebissonii (Meneg.) Ealfs. 



P. crassa de Bary. 



P. rupesfre Kiitz. 



Closterium lanoeolatum Kiitz. 



C. suhdirectum nov. sp. Frond about fifteen times longer than 

 broad, gently tapering, the middle portion nearly straight, 

 slightly curved towards the ends, which are truncate with 

 rounded corners, cytoderm finely striate, with three 

 distinct transverse sutures. 



Breadth 26-27 /x, length 390-400 fi. 



This is very like G. directum Arch., but larger and not so 

 finely striate. It is also larger than G. intermedium 

 Kalfs, and less curved, and difiers from any form of G. 

 didymotoeum Corda in being more slender. Figs. 10 and 

 16. Very sparingly. 



C. lunida Ehrenb. 



C. Gucumis Ehrenb. 



C. acerosum (Schrank) Ehrenb., var. elongatum nov. var. 

 Much narrower than the small examples of usual form, 

 and not at all striate. Sparingly. Breadth 15-16 [x, 

 length 290-300 ^l. 



G. strigosum Ehrenb. 



G. striolatum Ehrenb. Abundant. 



G. costatum Corda. 



G. acutum Breb. 



G. Dianse Ehrenb. Abundant. 



G. Jenneri Ralfs. Frequent. 



G. Venus Kiitz. Frequent. 



G. parvulum Naeg. 



G. Ehrenbergii Meneg. 



G. LeiUeinii Kiitz. Frequent ; breadth mostly 40-50 fi. 



G. Leihleinii Kiitz., var. eurtum nov. var. This was compared 

 with undoubted specimens of G. Leihleinii, and exactly 

 agreed with them in the central part of the frond, hut 

 differed as shown in the figure hy its shortened ends. It 

 looks like a miniature G. Ehrenbergii, many of which were 

 present of the usual size. Fig. 8. Breadth 46-48 fju. 



G. rostratum Ehrenb. 



G. rostratum Ehrenb., var. hrevirostratum nov. var. This is 

 a variety I have often noticed in other gatherings; it 

 differs from the usual form in its short and less attenuated 

 heak. Fig. 9. 



Pocidium noduloswn Kalfs. 



D. Areherii Delp. Only one specimen of this was seen. 



D. Trabecula (Ehrenb.) Naeg. This seems to be so variable 

 a species that I have figured a semi-cell of one of the 

 1889. C 



