256 Nicholson — On Graptolites. 



view of it (See Woodcut, Fig. 3). How remarkably similar are 

 the histological elements — perforations and fibres — of this species 

 with those (particularly the " mere pits ") oi Bhynchopora Gemitziana ! ' 



According to Mr. Davidson, "it is certain that no vestiges of 

 spiral coils have hitherto been noticed by any author " in species of 

 Cyrtina : ^ possibly they will always remain unnoticed in the so-called 

 Cyrtina septosa, M'Coy's Pentamerus carhonarius, and certain other 

 presumed congeners. However, be this as it may, Cyrtina heterodita 

 is undoubtedly a Spiriferid ; as one of my old specimens, of the set 

 which disclosed to me the apophysary system previously noticed, 

 exhibited the spiral appendages very distinctly. 



Spirifebina, D'Orbigny, 1847. — This genus, which was separated 

 by its author from Spirifer in a great measure on account of being 

 perforated, appears to have its nearest affinities to Cyrtina,. as typified 

 by C. heterodita. Both genera have the normal canal-system. In 

 Spiriferina the dental plates are not attached, as in Cyrtina, to the 

 median plate : the latter is large, situated between, and independent 

 of, the former, — as was shown in my previously cited paper of 1846.^ 



I urged sundry objections against Spiriferina in 1850, one of which 

 arose out of the mistake I committed in concluding that all the 

 Spiriferidce are perforated ; but I have for some time past thought, 

 with Mr. Davidson, who was not hampered with this error, that the 

 genus is a good one. 



XV. — On a new Genus of Gtbaptolites, with Notes on 



Eeproductive Bodies.* 



By Henky Alleyne Nicholson, D.Sc, F.G.S. 



Baxter Scholar in the Natural Sciences in the University of Edinburgh. 



(PLATE XI.) 



THE Graptolite which I am about to consider is perhaps one of 

 the most remarkable of all our known British forms, and was 

 originally described by Mr. W. Carruthers,^ under the name of Clado- 

 grapsus linearis. The genus Gladograpsus is one which was proposed 

 by Geinitz to include certain forms of Didymograpsus ; but Mr. 

 Carruthers seems subsequently to have seen that the reference of 

 G. linearis to this genus was inappropriate, as he has recently alluded 

 to it,^ under the title of Bendrograpsus linearis. The genus Dendro- 

 grapsus of Hall includes certain branching Graptolites, which are 

 peculiar to the Quebec group in America, and which do not occur, as 

 far as is yet known, in the Skiddaw slates— our undoubted repre- 

 sentative of the Quebec series. The genus, in fact, appears to he 

 characteristic of the Lower Llandeilo period, the only known British 



1 See a similar view of the histology of this species given in the " Ann. and 

 Mag. Nat. Hist.," 2nd Series, Yol. xvii. plate xii. fig. 11, 1856. 



2 See " British Carboniferous Brachiopoda," p. 68. 



3 See "Ann. and Mag. Nat. Hist.," Vol. xviii. p. 86; also pre-cited "Mono- 

 graph," p. 68 and 123. 



* Bead before the Geological Society of Edinburgh, March 21st. 

 6 Annals and Magazine of Nat. Hist., Vol. iii. No. 13. 

 6 Geol. Mag., Vol. IV., No. 2, p. 70. 



