24 Dr. 0. Herrmann — On the Dichograpticfre — 



It has been thought that the forms described by the author (loc. 

 cit.), constituting a continuous series of examples with from 5 to 14 

 branches, were to be regarded as individuals of different ages, the 

 highest number of branches indicating the greatest age. The author 

 regards this view as untenable. No difference is to be detected in 

 the thickness and length of all the branches, such as would occur if 

 any of them were formed subsequently to the rest, whereas it might 

 be expected that the supposed younger branches would be observable 

 when they had just sprouted, and before they reached the margin of 

 the disc. It is also difficult to imagine how any such subsequent 

 increase could be brought about, as the branches originate by bifurca- 

 tion, which usually occurs only at the top of a branch. But the 

 notion is disposed of by the fact that young individuals occur with 

 8, 9, and 12 branches, just as in full-grown examples. 



Dichograptus Kjerulfi is found in the lower part of the Phyllograptus- 

 shale (Kjerulf's Lower Graptolite-shales, Brogger's Etage 3b), and 

 occurs in great abundance in a thin bed in the Galgenberg, near 

 Christiania, associated with D. octobrachiatus (Hall), Didymograptus 

 constrictus (Hall), etc. 



5. Dichograptus Logani (Hall), Nich. 



Graptolithus {Loganograptus) Logani, Hall. 

 Graptolites {Didymograptus) Logani, M'Coy. 

 Loganograptus Logani, Lapw. 



Quebec Group, Canada ; Skiddaw Slates (lower part), N. England ; 

 Australia. D. Logani, Etheridge, Ann. Mag. N. H. ser. 4, vol. xiv. 

 pi. hi. fig. 12, is doubtful. 



5 6. Dichograptus Logani (Hall.), var. australis (M'Coy). 

 Grapt. (Didymogr.) Logani, var. australis, M'Coy. 



Arenig, Australia. 



From Dichograptus new forms may proceed by the development 

 of branchlets upon the primary branches. These form — 



Genus XV. Clematograptus, Hopkinson. 

 Hydrosoma much ramified, bilaterally subsymmetrical. From a 

 short funiculus issue a great number of primary branches, from 

 which numerous branchlets spring on one or both sides, at irregular 

 distances, often closely packed together. Hydrothecae as in Dicho- 

 graptus. No central disc. 



1. Clematograptus implicatus, Hopk., Lapw. 



Loganograptus ? implicatus, Hopk. 

 Middle Arenig, Wales. 



2. Clematograptus multifasciaius (Hall), Hopk. and Lapw. 



Graptolithus multifasciatus, Hall. 

 Hudson Eiver Group, New York. 



D. (L.) Logani, Etheridge (Ann. Mag. N. H. ser. 4, vol. xiv. pi. iii. 

 fig. 11), from Australia, probably belongs to this genus. 



Genus XVI. Clonograptus, Hall. 



Hydrosoma bilaterally subsymmetrical, consisting of more than 

 four simple branches produced by dichotomous division. The spaces 



