lxxxvi BRITISH GRAPTOLITES. 



The classification of the Rhabdophora, proposed by 

 „. , . , Lapwovth in 1873, is adopted, but in addition a new sub- 



Hopkinson and >- . 



Lwpworth, order, entitled Cladophora, is proposed by Hopkinson to 



" The Graptolites of embrace all the remaining Graptolithina. This Sub-order is 



the Arenig and divided into two sections: (1) Thamnoidea, with its family, 



Llandeilo Eocks of St. Thamnoo . raptidfe and its ~ enera Thamnograptus and Butho- 



David's,'" Quart, Jourii. ° { b * / 



0_ | g , ] . , • graptus, and (2) Dendroidea, with its families rtuograptiaaB 



and Callograptidse, the latter family including the genera 

 Dendrograptus, Gallograptus, and Dictyograptus, with its new Sub-genus Desmo- 

 graptus. 



An attempt is made to render the nomenclature of the Graptolites more 

 uniform, by employing the termination "graptus " in the names of all the genera, 

 as, for example, Bastrograptus, Gladiograptus, etc. 



Terminology. — A section of the paper is devoted to the terminology employed 

 in describing the Graptolites. The "sicula" is carefully distinguished from the 

 "radicle"; but the latter term is still employed in Hall's original significance, for 

 the " proximal prolongation of the virgnla " whatever its form. The various 

 forms of appendages — viz. 1, lateral or peridermal; 2, ventral or thecal; 3, proximal 

 and mesial; 4, apertural ; 5, proximal; or 6, radicular — are defined and distinguished. 



Description of Species. — The descriptions of the species are concise and accurate, 

 but the figures are poor, and their identification is in some cases a matter of 

 difficulty. The following genera, species, and varieties are given as new : (1) 

 Didymograptus sparsus, (2) D. Nicholsoni, (3) I), euodus, (4) D. indenius var. 

 nanus, (5) D. furcillatus, (6) Tetragraptus Halli (= T. serra), (7) T. Hicksii 

 (Azygography), Clematograptus n.g., (8) G. implicatus, (9) Climacograptus ccelatus, 

 (10) G. confertus, (11) Phyllograptus stella (= Didymog. gibberulus), (12) Trigono- 

 graptus truncatus, (13) Ptilograptus cristula, (14) P. Hicksii, (15) P. acutus, 

 (16) Dendrograptus persculptus, (17) D. arbuscula, (18) D. Ramsayi, (19) D. 

 serpens, (20) D. flexuosus var. recurvus, (21) Gallograptus radiatus, (22) C. 

 radicans, (23) Dictyograptus Homfrayi, Desmograptus n.g., (24) D. cancellatus. 



Other species described and figured are : (25) Didymograptus affinis, (2G) D. 

 extensus, (27) D. indentus, (28) D. patulus, (29) I). Murchisoni, (30) D. pennatulus, 

 (31) Tetragraptus quadribrachiatus, (32) T. serra, (33) Nemagraptus capillaris, 

 (34) Dicellograptus moffatensis, (35) Diplograptus dentatus, (36) D. foliaceus, (37) 

 D. tricornis, (38) Glossograptus ciliaius, (39) Trigonograpius ensiformis, (40) Dendro- 

 graptus diffusus, (41) D. divergent, (42) D. flexuosus, (43) Gallograptus elegans, (44) 

 G. Salteri, (45) Dictyograptus irregularis. 



Range and Distribution. — The range and distribution of these species are 

 discussed. The division of the Arenig as proposed by Hicks into Lower, Middle, 

 and Upper is adopted, and the Arenig and Llandeilo beds are compared as 

 respects their Graptolites with their American and British equivalents. 



