82 Linnean Society. [Dec. 1, 



the exposed banks, but was most evident on the stones nearest the 

 water's edge. On examimng the stones with a pocket-lens, their 

 surface appeared covered with acicular crystals, and hence it was 

 at first concluded that the incrustation arose from the crystalliza- 

 tion of some salt abounding in the waters. On procuring, however, 

 some stones from the water itself, they presented on their surfaces 

 the filaments of a minute conferva, which appeared to be the source 

 of the white crust ; but as the existence of the conferva would not 

 explain the crystalline appearance, it was examined under the micro- 

 scope, and was found to proceed from minute acicular bodies about 

 jJ,^) th of an inch long and g-oV o*-^ °^ ^^ ^"^^^ broad, which were most 

 of them arranged in a stellate form, although many were scattered 

 in all directions. Running under the whole were the filaments of a 

 minute conferva, on which the acicular bodies rested. 



In Greville's Scottish Cryptogamic Flora, similar bodies are re- 

 ferred to the genus Exilai'ia, but Dr. Lankester describes the stellate 

 arrangement of the aciculse as giving to those examined by him a 

 different character from E. fasciculata. Hooker, in his continuation 

 of Smith's 'English Flora,' has placed Greville's name as a synonym 

 of Diatoma truncatum, from which D. fasciculatiim is believed not to 

 be distinct. 



In Ehrenberg's work on the Infusoria, these bodies are figured 

 and described (p. 11. tab. xvii.) as Polygastric animalcules of the 

 family Bacillaria. The genus to which they belong is Synedra, and 

 the Bpecies which they most closely resemble is the Synedra Ulna, 

 which is characterized by being striated, with linear corpuscles, 

 straight, truncated at the sides, flat on the back and belly, with the 

 apex a little dilated as the individuals become aged. The bodies 

 from the Annan are not striated, nor are their ends dilated, although 

 they appear to be fuU-grown. The siliceous skeletons in which these 

 little animals are invested account for their white appearance. Al- 

 though similar bodies have been often described both as plants and 

 animals, the author believes that no notice has been taken of their 

 producing the phsenomenon here described. 



Read also, " Observations on the Genus Derbe of Fabricius." 

 By John O. Westwood, Esq., F.L.S. 



After noticing the recent memoirs by Messrs. Percheron and 

 Boheman on this little-known Fabrician genus, and its very close 

 relationship to Otiocerus and Anotia of Kirby, the author states that 

 the Fabrician type of the genus, D. hcemorrhoidalis, is quite distinct 

 from the group described as such by the two first-mentioned authors. 



