HISTORY OF RESEARCH. cv 



expansum, D. Websteri, D. tenellum, D. splendens, D. pergracile; Galyptograptus 

 cyathiformis, G. subretiformis, C. micronematoides, G. ? radiatus, Bhizograptns 

 bulbosus, Acanthograptus Grant!, A. pulcher ; Inocaulis plumulosus, I. bellus, I. 

 divaricatus, I. problematicus, /. diffusus, J, cervicornis, I. phycoides, /. ramu- 

 losus ; Thamnograptus bartonensis, T. multiformis (not a Thamnograptus), Ptilo- 

 graptus foliaceus ; Cyclograptus n.g., G. rotadentacus. 



The new species are mainly founded on the features presented by their 

 general outlines. 



188 5 In the year 1885 Herrmann published a monograph on 



Herrmann, the family of the Dichograptida?. This work is valuable as 



" Die Graptolitheii- giving a fairly complete summary of our knowledge of the 



familie Dichograptidse, Graptolites in general, and of the Dichograptida? in particular, 



Lapw.," 'Nyt Map:, for , . . . 



J: . • , °. at the time it was written. 



Naturvid., bet. xxix. . 



Classification. — The family Dichograptidas includes, 



according to Herrmann, sixteen genera, which he groups as follows : 1, Didymo- 



graptus ; la, TricJiograptus ; lb, Bryograptus ; lc, Ptevograptus ; Id, TJenrogvaptus ; 



2, Janograptus ; 3, Tetragraptus ; 3a, Schizograptus ; 3b, Trochograptus ; 3c, Gteno- 



gr aphis ; 3d, Type Gr. Bichardsoni ; 3e, Holograptus ; 3f, Goniograptns ; 4, Dicho- 



graptus ; 4a, Glematogvaptus ; 5, Glonograptus. 



He gives all the previously described species of each genus, and transfers some 

 species from genera in which they had been placed by previous authors to other 

 genera. The only new species described by Herrmann is Pterograptus ? dilaceratus, 

 from the Phyllograptus shales of Norway. 



Organisation. — In a chapter dealing with the organisation and economy of the 

 Graptolites, the sicula is described, and its function as an organ of attachment 

 denied. The question of the " angle of divergence " of the stipes is discussed in 

 much detail, and Herrmann suggests, for the first time, the employment of the 

 ventral instead of the dorsal angle as the conventional " angle of divergence," a 

 plan which has since been generally adopted by Graptolithologists. He con- 

 siders that the Graptolites probably lived with the sicula below and the branches 

 growing upwards. He supports Holm's opinion that in some cases, at any rate, the 

 " funicle " bears thecas ; and gives additional examples. He deals with the function 

 and development of the central disc at considerable length ; attaches consider- 

 able importance to Hopkinson's discovery of an apparent dividing septum between 

 the theca and common canal, and agrees with him that it places the " hydrothecal " 

 nature of the cells beyond doubt. 



I 885 - Roemer describes and figures several species of Grapto- 



Jioemer, lites from the greenish-grey Graptolithen-Gestein of North 



', ' ' Germany. These are: M. ludensis, M. testis, M. scanicus, 



'Palaeont. Abh. v. J 



Dames unci Kayser,' Retiolites Geinitzianus, and two unidentified species of Mono- 

 bd. ii, heft 5. graptllS. 



V 



