317 
valve with its hoop is partially embraced by, or let into, the 
hoop of the other valve. One valve and hoop has of course 
been produced by division from the other valve, and to this 
latter the name of primary valve was given, whilst the other 
was called secondary. Dr. Macdonald illustrates in the case 
of Biddulphia the formation of the new valve and hoop, one 
within each of the old pair, their growth and separation ; and 
he points out that the new valves must be ever smaller and 
smaller. How then is the size of the species maintained ? 
An answer is found in Thwaites’ observation, the author 
remarks, who noticed that the sporangial frustrule was so 
much larger than the parent, and whose observation was 
misinterpreted by Smith in the other direction, viz., that the 
parents were very much larger than the sporangial product. 
The Genus Lophiostoma . — A descriptive synopsis of the 
twelve British species of Lophiostoma (Fungi) by M. C. 
Cooke is published in the ‘ Transactions ’ of the Botanical 
Society of Edinburgh for 1868, just issued to the fellows It 
is accompanied by a coloured plate of the asci and spores of 
the majority of species, magnified from 300 to 400 diameters. 
Greenland Diatoms. — Dr. Dickie has examined the Algae 
collected in Greenland by Mr. Robert Brown, and enume- 
rates the following : 
Epithemia ocellata, Kiitz. 
Eunotia monodon, Ehr. 
Svnedra ulna, Ehr. 
Navicula dicepliala, Kutz. 
Stauroneis anceps, Ehr. 
Stauroneis gracilis, Ehr. 
Cocconema lanceolatum, Ehr. 
Meridion circulare, Ag. 
Odontidium mesodon, Kutz. 
Tabellaria flocculosa, Kiitz. 
Himantidium majus, Sm. 
Arachnoidiscus Ehrenbergii. 
Actinocyclus undulatus. 
Biddulphia Roperiana. 
Cocconeis scutellum. 
The few species noted here are to be considered as supple- 
mentary to Dr. LyalFs Diatomacese recorded by Mr. Kitton 
in the ninth volume of the ‘Journal of the Linnean Society.’ — 
Trans. Bot. Soc. Edinb., 1868. 
Cocconeis Grevillei. 
„ undulata? 
Podosphenia Ehrenbergii. 
„ gracilis. 
Podosira hormoides. 
Rhabdonema arcuatum. 
„ minutum. 
Synedra affinis. 
„ investiens. 
Nitszchia „ 
Triceratium arcticum. 
Coscinodiscus eccentricus. 
Grammatophora marina. 
Isthmia nervosa. 
