362 SCIENCE PROGRESS. 



" biserial chamber," thus producing a connection between 

 the various parts of the polypary. These features are 

 common to all the forms described by the author, but the 

 forms differ in other respects. In Climacograptus scalaris 

 Linn, and Climacograptus internexus Tornq. the biserial 

 chamber communicates with two uniserial canals separated 

 from one another by a median septum. In Diptograptus 

 palmeus Barr. the septum scarcely extends through half the 

 thickness of the polypary, whilst in Cephalograptus cometa 

 Gein. it is " reduced to a narrow 7 fold of the obverse peri- 

 derm," and in Diptograptus bellutus Tornq. it is altogether 

 absent. 



Two papers by Wiman (10) treat of the structure of the 

 Diptograptidce and of Monograptus. Notices of these papers 

 by E. M. R. Wood and G. L. Elles appear in the Geological 

 Magazine for 1895, p. 431. The accounts of the structure 

 of the sicula, and of those parts of the polypary immediately 

 in contact with it, are largely confirmed by Holm in a paper 

 to be noticed immediately, but the statement that the Dip- 

 tograptida; are monoprionidian because the sicula gives rise 

 to only one bud (which is on the right hand side) involves 

 a special use of the term monoprionidian which will hardly 

 meet with general acceptance. 



A most important paper by Gerhard Holm must now be 

 noticed (11). Holm has had the advantage of studying 

 some beautiful material derived from the J^aginatus-Yimestone 

 (of Areing age) from various localities in the northern part 

 of the Island of Oland ; the graptolites of this limestone he 

 has succeeded in freeing from the matrix, thus rendering 

 them serviceable for detailed study. (The method of re- 

 moving the matrix is described by Holm in an article in 

 Bihang K. Vetensk. Akad. HandL, Bd. xvi., 1890.) In the 

 present paper he gives reasons for supposing "that the 

 earlier development of the proximal part — the first three 

 thecae — in all the bilateral or diprionidian forms of graptolites 

 is in the main the same, and has taken place through the 

 formation of only one bud on one side of the sicula — -or first 

 theca, as I believe it is — which side is always the same in 

 relation to the later development of the polypary. From 



