22 Dr. 0. Herrmann — On the Dichogr apt idee — 



1. Dichograptus octobracliiatus (Hall), Nich., (M'Coy), Lapw., 

 Brogg. (Fig. 7.) 



Fig. 7. Dichograptus octobrachiatus, Hall, from the Pliyllograptus-shales, 

 Galgenberg, Christiania (natural size) . 



Graptolithus octobrachiatus, Hall. 



Graptolites (Didymograptus) octobrachiatus, M'Coy. 



Loganograptus Kjeru'fi, Herrm. ex parte. 



The central disc may or may not be present. In the typical con- 

 dition the species has eight branches, but specimens are frequent 

 with more or fewer branches. 



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

 Phyllograptus-shales, Norway ; Arenig, Australia. 



2. Dichograptus octonarius (Hall), Lapw. 



Graptolithus octonarius, Hall. 

 Central disc unknown. Quebec Group, Canada. 



3. Dichograptus Sedgwichii, Salt. (Figs. 6a, Qb.) 



Figured but not described by Salter (Q.J.G.S. vol. xix. p. 138). 



The author describes the species : — 



In the typical condition the hydrosoma consists of eight simple, 

 curved branches, which are arranged as in D. octobrachiatus, Hall. 

 There is in this species the same variation in the number of branches 

 as in D. octobrachiatus, which is its nearest ally, the differences be- 

 tween them consisting in the curvature of the branches, and the 

 habit of the hydrothecae. Of the latter there are eight in a length 

 of ten millim. Their lower border is curved and forms with the 

 axis an angle of 10° — 12° at the proximal end, of about 30° at the 

 distal end. The apertural angle is about 90°, and the hydrothecEe, 

 which are about one-half longer than broad, are half free, appeariug 

 as pointed, nearly perpendicular teeth (Fig. Qb). No central disc has 

 been observed either in English or Norwegian specimens. 



Skiddaw Slate (lower part), N. England; lower part of Phyllo- 

 graptus-sh&les, Norway. 



4. Dichograptus Kjerulfi (Herrm.) (Woodcut, p. 23, Fig. 8). 



Loganograptus Kjerulfi, Herrm. ex parte. 



In 1882 (Nyt Mag. for Naturv. xxvii. pp. 341-362) the author 

 described and figured, under the name of Loganograptus Kjerulfi, a 

 number of foruis which subsequent study showed him must be 



