ON SOME NEW SPECIES OE CLADOPHORA. 



171 



Appendix. 



Oa the Cladophora (Ilopk.) or Dendroid Graptolites collected by 

 Professor Keeping in the Llandovery Modes of Mid Wales. By 

 Chas. Lapworth, Esq., F.G.S. &c. 



[Plate VII.] 



The forms of Cladophora collected by Professor Keeping from 

 the Llandovery rocks of Cardiganshire are, regarded collectively^ of 

 a type almost new to British palaeontology. Although intimately 

 allied to the well-known dendroid species of the Quebec and Arcnig 

 formation, they are very distinct in their minor features. They are 

 essentially of a Silurian (Upper) facies, and they remind us strongly 

 of a group recently made known to us through the researches of Mr. 

 Spencer, of Toronto, which characterizes the Clinton and Niagara 

 Groups of New York and Upper Canada *. 



None of our examples shows the complete polypary, or affords dis- 

 tinct proof of the presence of all the more minute classificatory 

 features ; but there is satisfactory evidence of the presence of at 

 least four distinct genera and seven species. The genera repre- 

 sented are Dictyonema, Hall, Calyptograptus, Spencer, Acantho- 

 graptus, Spencer, and Odontocaulis, Lapw. Dictyonema is a well- 

 known British genus ; the remainder are new to British palaeon- 

 tology. Calyptograptus and Acanthograptus have been already 

 briefly noticed from American strata by Mr. Spencer, but have not 

 hitherto been figured. Odontocaulis is a new genus, of a peculiar 



Of the seven distinct species recognizable, four (viz. Dictyonema 

 corrugatellum, Calyptograptus plumosus , C. digitatus, and Odontocaulis 

 Keepingii) are as yet peculiar to the Mid- Wales area. The remaining 

 three have already been recognized by niyself in the Silurian rocks 

 of the south of Scotland. Dictyonema venustum certainly occurs in 

 the Upper Gala group of Selkirkshire (Llando very-Tar annon), and 

 doubtfully in strata of a little older date in the Girvan area. 

 Dictyonema delicatalum has been met with in the Llandovery (Lower) 

 of Shalloch Forge, near Girvan. Acanthograptus ramosus occurs 

 also in the Girvan area, at the base of the representative of the 

 Tarannon Shales. 



We do not yet know enough of the Cladophora of North America 

 to enable us to identify any of these Mid-Wales forms with corre- 

 sponding species already described or figured from the Silurian strata 

 of that continent. 



Genus Dictyoneha. 



Dictyonema, Hall, Palaeontology, New York, vol. ii. 



1. DicTTONEiiA venustum, sp. nov. Plate VII. figs, la-lc. 



Polypary cyathiform in the growing state, at least 10 inches in 

 transverse diameter. Branches uniform, about one eightieth of an 



* "Graptolites of the Niagara Formation," by J. W. Spencer, F.G.S., Canadian 

 Naturalist, 1878-9, pp. 457-463. 



