174 



C. LAPWOETH Q~N SOME NEW 



uniting the branches. In the mode of branching and in the form of 

 the calycles it approaches the genus OdontocauKs, to be presently 

 described, from which, however, it is easily separated by its short 

 non-poly piferous stem. 



Horizon and Locality. Llandovery of Devil's Bridge, Aberyst- 

 wyth. 



5. Calyptogeapttjs ? dioitatus, sp. nov. Plate YII. figs. 6<z-66. 



Polypary short, composed of numerous compound branches about 

 of an inch in width, dividing irregularly, and terminated distally 

 by a group of palmatifid branchlets about one tenth of an inch in 

 length. Calycles of the type of those of Callograptus, about 50 to 

 the inch. 



The magnified drawing gives a fair idea of the external features 

 of the only specimens seen, which are mere fragments. The 

 proximal extremity of the stem is unknown ; but the irregular mode 

 of subdivision of the branches is different from what generally 

 occurs in Dictyonema and its allies. There is a doubtful appearance 

 of reticulation among the secondary branches. 



The most remarkable feature of this form is the strange digitate 

 character of the final spine-like branchlets. Mr. Spencer has noticed 

 the same feature in the genus Rhizograptus (op. cit. supra, p. 461), 

 to which it is possible the present species properly belongs. 



Horizon and Locidity. Llandovery of Devil's Bridge, Aberyst- 

 wyth. 



Genus Acanthogeaptus, Spencer. 



Gen. char. " Polypary shrublike, consisting of thick branches, 

 principally rising from near the base, with little divergence and 

 some bifurcations. One side of the branches is furnished with 

 prominent .spines or denticles, which appear to mark the cell- 

 apertures. Test corneous and indistinctly striated." 



" This generic form resembles Dendrograptus, but is stronger and 

 more bushy than species of that genus, and has conspicuous spines 

 indicating a different cell-structure " (Spencer, op. cit. p. 463). 



The foregoing is Spencer's diagnosis of his new genus Acantho- 

 graptus. I have provisionally assigned to it one of Professor 

 Keeping's species, which answers fairly enough to Spencer's defini- 

 tion. It is impossible to ascertain from Spencer's diagnosis whether 

 the denticles that ornament the calycles are horizontal or inclined. 

 If the former be the case, I suspect that Acanthograptus will be found 

 to lie somewhere near Thamnograptus of Hall, in which the calycles 

 are provided with long projecting spines, and that the present form 

 must be regarded as the type of a new genus. 



Acanthograpttus occurs both in the Bala and Llandovery strata 

 of Girvan, South Ayrshire, where, however, it is an uncommon 

 fossil. None of the species collected by myself from the Scottish 

 locality appears to be precisely identical with the Mid- Wales form. 



6. Acanthogeapttjs eamosus, sp. nov. Plate VII. fig. 5. 

 Polypary short, shrublike, with thick rigid branches, repeatedly 



