NOTES AND COMMENTS. 



95 



the gelatinous or protoplasmatic material outside the framework or 

 skeleton. Very many genera besides Melosim and Cyclotella are known 

 to possess similar spinous processes, which are stiff, non-retractile, 

 and arranged symmetrically around the valves. The same kind of 

 perfectly rigid spines are also a characteristic formation of many 

 desmids — Micrasterias, Artlirodesmns, Epithemia, Stephanosia, and Achnan- 

 tkidinm. These appendages, however, bear no resemblance to the 

 well-known pseudopodia of the lower Protozoa, which are most un- 

 deniably organs of locomotion and prehension.'" Mr. Hogg continues 

 with a readable review of the theories of the movement of diatoms, 

 which we commend to the notice of all interested in the subject. 



The Journal of Botany makes the welcome announcement that 

 Messrs. J. Britten and G. S. Boulger are preparing to issue in 

 separate form the Biographical Index of British and Irish Botanists, 

 which has for several years been running through the journal and 

 has lately been completed. The Index is to appear in June, and 

 will extend to the end of 1891. 



A STUDY of the Speeton Clay and its Russian equivalents has 

 led Professor A. Pavlow to publish a long memoir on the various 

 forms assumed by the "guards" of Belemnites in the new number 

 of the Bulletin de la Soaete Imperiale des Natuvalistes de Moscoii (vol. for 

 1891, Nos. 2, 3). Many good figures and detailed descriptions of 

 Cretaceous species are given, and the memoir concludes with some 

 general observations on the classification of these fossils. The 

 "guards" of Belemnites seem to be of much value to the strati- 

 graphical geologist — " medals," as Mantell would term them — but 

 it is to be regretted that they furnish so slight an idea of the 

 characters and evolution of the cephalopods to which they originally 

 belonged. We are glad to notice that our countryman, Mr. 

 Lamplugh, is co-operating with Professor Pavlow in his researches. 



We regret to learn from recent letters from Dr. J. W. Evans, the 

 geologist with the Matto Grosso Expedition, that the party has just 

 returned to Europe after a somewhat disappointing journey. This 

 seems to have been mainly due to the action of one of the recent 

 Governments of Brazil, which refused to ratify the concession made 

 by the late Emperor. The district in which Dr. Evans spent most of his 

 time was not a profitable locality geologically, consisting of enormous 

 tracts of crystalline schists, clay slates, and sandstones ; these have 

 so far not yielded a single fossil, and igneous rocks are represented 

 only by seams of ashes in the slates. A few bands of limestone were 

 met with, but they are all unfossiliferous. The most interesting 

 part of Dr. Evans' journey seems to have been an ascent of the 



