NOTICES OF SERIALS. 67 



every species of each genus, and in one assumes a form quite different from 

 the ordinary. The sessile form of avicularium may be subdivided into 

 the projecting and the immersed. Of these, the latter is the more exten- 

 sively distributed; it is placed either at the angles or margin of the cells, 

 usually of their anterior aspect, but sometimes on the posterior; instances 

 of this latter may be found in Cabarea nuda, and the genus Retaphora. 

 The importance of a due attention to these organs as affording specific 

 and even generic distinctions, may be best appreciated in the difficult and 

 hitherto much confused families of Flustradae— Membraniponda, and es- 

 pecially of the Celliporidce, Escharadoe, and Selenaridce. In Lepralia 

 these organs are of the utmost importance and easily available. The mode 

 in which Mr. Busk has employed this character may be seen in his " Cata- 

 logue of British Marine Polyzoa," published by the British Museum. 

 (Queckett, John) On the Minute Structure of a peculiar Combustible 

 Mineral from the Coal Measures of Torbane Hill, &c. This mi- 

 neral, our readers may remember, has lately excited considerable at- 

 tention in the scientific world, and a trial, " second to few in importance, 

 has lately taken place in Edinburgh, having for its object the determination 

 whether the Torbane Hill mineral should be called a coal or not, and 

 whether it should be included in the missive of agreement for a lease, and 

 let as coal." On the trial, 78 witnesses were examined — 33 for the plain- 

 tiff, and 45 for the defendant — who might be differently classified. This 

 memoir only enters into the evidence offered by the microscopists examined, 

 among whom was its accomplished author, and has for its object to prove 

 — " That the Torbane Hill mineral is not, microscopically speaking, a 

 coal ; that it is not like any of the combustible substances used in this 

 country as coal ; and though possessing some of the properties of coal, it 

 is, notwithstanding, a mineral sui generis, having a basis of clay which is 

 strongly impregnated with a peculiar combustible principle; and that when 

 plants are found in it, they are accidental, and have no more been con- 

 cerned in the formation of the mineral, than has a fossil bone in that of the 

 rock in which it may have been imbedded." (Gregory, William) New 

 Forms and Varieties occurring in the Diatomaceous Earth of Mull, with 

 Remarks on the Classification of the Diatomaceaa. Translations — (Virchow, 

 Rud.) On the Irratibility of Ciliated Cells ; (Tulasne, M. L.-R.) On the 

 germination of the Spores of the Uredinece, extracted from " Comptes 

 Rendus," torn. xxxv. Reviews — (Fresinius, Dr. George) Beitrage Zur 

 Mycologie (contributions to Mycology) ; (Unger, Dr. F.) Botanical 

 Letters to a Friend. Notes and Correspondence. Proceedings of 

 Societies. 



