HISTORY OF RESEARCH, lxxxix 



only, and this theoretically invariably originates a single ccenosarcal tube." In 

 Diplograptus, Vleurograptus, etc., this is divided immediately after origin; but 

 in Tetragraptus division takes place twice. The horizontal bar between the 

 proximal ends of the two pairs of primary branches in Tetragraptus, etc., is Hall's 

 true "funicle," and is the only non-polypiferous portion of the polypary. 



Lapworth considers that the structure of Dimorphograptus '* lends suppori to 

 the theory that the Monograptidae are the direct descendants of the Diplograptidae, 

 and not of any of the compound monoprionidian genera." 



Range and Distribution.— -The paper concludes with a general account of the 

 range and distribution of the Monograptidse in Britain and abroad. The author 

 recognises three successive specific groups, viz., those of the (1) Birkhill Shales 

 (= Ooniston Mudstones = Lower Llandovery), (2) (Jala and Girvan, (3) Upper 

 Silurian of Riccarton and the Pentland Hills (= Coniston Flagstones and Wenlock 

 and Ludlow Beds). Each of these possesses a well-marked and distinctive assem- 

 blage of Monograptidae, and the vertical distribution of species in Scotland is in 

 complete agreement with that in England, Ireland, and Europe. 



He emphasises the fact that not a single species of any genus of the Mono- 

 graptidae occurs in beds lower than the Bala limestone and therefore that the 

 family is exclusively a Middle and Upper Silurian one. 



A complete illustrated list of the Scottish Graptolites 



Lapworth recognised in 1876 was given by Lapworth in the ' Catalogue 



' Catalogue of Western of Western Scottish Fossils ' prepared for the Meeting of the 



Scottish Fossils.' British Association at Glasgow. Among them were several 



"Graptolites. new S p 0C j es which were figured but not described. It will 



suffice here to mention the figured forms then new to science: (1) Diplograptus 

 pristis var. truncatus, (2) D. foliaceus var. calcaratus, (3) />. perexcavatus, (4) IK 

 qnadrimucronatus var. spinigerus, (5) D. aculeatus, (6) Glima cograptns tubuliferus, 

 (7) G. bicomis var. tridentatus and (8) var. peltifer, ( ( .>) G. Scharenbergi, (10) G. 

 coelatus, (11) Gamograptus nitidulus, (12) G. pertenuis, (13) G. explanatus, 

 (14) Amphigraptus radiatus, (15) Didymog raptus superstes, (16) Dicranograpttts 

 ziczac and (17) var. minimus, (18) Vicellograptus pumilus, (19) D. caduceus, 

 (20) l>. Forchammeri var. articulatus and (21) var. flexuosus, (22) Gorynoides 

 curtus, (23) Thamnograptus scoticus, and (24) Dictyograptus moffatensis. 



Two papers on the Silurian rocks of Dumfriesshire and 

 1874-6. their fossil remains were read by Dairon before the Geological 



, ' . Society of Glasgow in 1874 1876. [n these a general account 



" Notes on the Silurian 



Rocksof Dumfriesshire of fche Graptolites is given, their alii.,, ties, structure, develop- 



an.l their Fossil llient.etc. A II limber of species ;uv given and figured, anil 



Remains," 'Trans. three new ones are figured but not described: (I) ThamiW- 



Oeoi Soc. Glasgow.' araptus crucifer, (2) Eetiolites branchiatus, and (3) Dicellog. 

 guilloche. 



