654 J. HOPKINSON AND C. LAP WORTH ON THE GRAPTOLITES OP 



Nemagraptus which occur in South Scotland, and also in those 

 which belong to the genus Coenograptus of Hall. In all these the 

 primary branches originate from approximately opposite points mid- 

 way along the sicula, which forms a remarkable "radicular" or 

 proximal bar in the adult organism, a feature unknown in the 

 Khabdophora outside the limits of these two most intimately allied 

 genera. 



In another respect, also, the present examples unfortunately re- 

 semble those figured by Dr. Emmons. They show nothing that can 

 be referred to the denticles or hydrothecal apertures, beyond a certain 

 ill-defined crenulation of the margins of some of the branchlets. 

 This, however, is the rule both in Nemagraptus and Coenograptus. 

 The latter especially, though both its primary and secondary 

 branches are furnished with hydrothecaa throughout the whole of 

 their extent, rarely affords conclusive evidence of their presence on 

 the chief branch until the last branchlet has been thrown off. This 

 circumstance was pointed out by Dr. Emmons in connexion with 

 Nemagraptus; and Professors Hall and Nicholson both make the 

 supposed non-polypiferous character of the proximal portions 

 of the main branches the chief characteristic of the genus Cceno- 

 graptus. 



Log. Upper Arenig, Llanvirn Quarry. 



Family DICBANOGBAPTIDJE, Lapworth. 

 Genus Dicellograpttts, Hopkinson. 



Dicellograpttts moppatensis, Carruthers, sp. PL XXXIV. figs. 

 3 a, 3 b; PI. XXXV. figs. 5 a, 5b. 



1858. Didymograpsus moffatensis, Ca;rr. Trans. E. Phys. Soc. Edin. 



p. 469, fig. 3. 



1859. Graptolithus divaricatus, Hall, Pal. N. York, vol. iii. pt. 1, 



p. 514, figs. 1-4. 



1870. Didymograpsus divaricatus, Nicholson, Ann. & Mag. Nat. 



Hist. ser. 4, vol. v. p. 350, pi. vii. figs. 4, 4 a. 



1871. Dicellograpsus moffatensis, Hopk. Geol. Mag. vol. viii. p. 25, 



pi. i. figs. 4 a, 4 6. 

 Branches somewhat rigid and slightly curved, diverging from each 

 other at an angle of from 30° to 90° ; axil furnished with a 

 well-marked radicle and two short lateral spines ; sicula short 

 and stout, scarcely ever visible ; hydrothecaB 20 to 25 to the 

 inch, isolated and strongly incurved for the last third of their 

 length ; interspaces very oblique, usually compressed to a mere 

 slit. 

 The specimens of this species, collected from the Llandeilo beds of 

 Abereiddy Bay, are very indifferently preserved, and it is scarcely 

 possible to make out more than the general characteristic shape of 

 the polypary. They all belong to the well-marked variety divari- 

 catus of Professor Hall, in which the branches are straighter and 



