cxvi BRITISH GRAPTOLITES. 



During this same year, also, several important papers were published dealing 

 with (ho details of the structure of Dijrfograptus and Monographic. 



The first paper was one by Tornquist, " On the Structure 

 „.. ' of some Di prion idae." By means of transverse and longitudinal 



Turin/ /list, l J o 



"Observations on the sections of specimens preserved in iron pyrites he worked out 



Structure of some many details of structures previously obscure. Like Moberg 



Diprionidse," ' Lunds ] 1C distinguishes carefully between the two aspects of the poly- 



Univ. Arsslv-rift; y Qv fchege ho adopts the terms " obverse " (in which 



\)(\ XXIX * 



the sicula is completely visible) and " reverse " (in which the 

 sicnla is partly concealed from view). The row of thecre which contains the first 

 theca is called by him the " primordial " series, and the other the " second " series. 



As regards the development of the first thecae he shows that the sicula gives 

 rise (on the left side in the obverse aspect) to a small lobe which develops into a 

 conical space similar to that of the sicula, but " shorter, and communicating 

 with the common cavity of the rhabdosoma." This he distinguishes as the " con- 

 necting canal." " Surrounding not only both sides of the sicula, but also its 

 reverse wall," there is an undivided space which he calls the " biserial chamber." 

 The structure of the median septum as respects its complete or incomplete nature, 

 as shown in certain species, is also worked out. In all cases the author apparently 

 implies that each theca is developed from the theca immediately below belonging 

 to the same series. 



These details are worked out in the case of Climacog. scalaris, C. interne-sens, 

 Viplog. bellulus, D. palmeus, and Gejphalog. cometa. 



The structure of Dvplogra/ptus was still further elucidated 



Wiman D J Wiman during the same year. He obtained his results by 



" Ueber Diplo^rapti- carrying out the methods previously employed by Holm in 



dae," ' Bull, of the Geol. the case of Dictyonema and Retiolites, namely, of completely 



Instit. of Tjpsala,' no. 2, isolating- the specimen from the matrix. 



The most important discoveries made known by Wiman 

 in this paper are with reference to the sicula and the virgula. 



The sicula is shown to consist of two parts : (a) a proximal cup-like portion 

 similar in structure to an ordinary theca and possessing growth lines, and (l>) 

 " a distal portion consisting of coarse, longitudinal branching or anastomosing 

 thickenings or threads." The apertural spines (two in number) of the sicula are 

 also described, and are shown to be flat, not cylindrical. The bilateral symmetry 

 of the sicula thus produced reminds one of a " Bryozoan rather than a modern 

 Hydroid polypary." 



The relations of the virgula, as then accepted, are fnlly discussed, and it is 

 shown to consist of two distinct and separate parts, the distal part (or virgula 

 proper as now understood), having its origin in the union of the longitndina 

 lines of the distal portion of the sicnla. 



