THE ARENIG AND LLANDEILO ROCKS OF ST. DAVID'S. 661 



Suborder CLADOPHORA, Hopkinson. 



Section Dendroidea, Nicholson. 



Family PTILOGEAPTID.E, Hopkinson. 



Genus Ptilograptus, Hall. 



Ptilograptus cristula, Hopk., sp. nov. PI. XXXYI. figs. 2 a 

 &2b. 



Brit. Assoc. Eeport for 1872. 



Very slender, bipiimate ; stem waved or zigzagged, about the same 

 thickness as the branches ; primary branches alternate, diver- 

 ging from the main stem at an angle of about 45°, and occasion- 

 ally giving off short secondary branches in a similar manner 

 and diverging at the same angle ; hydrothecse not perceptible. 



The only specimens we have are probably merely fragments ; and 

 therefore this description can only be considered provisional. The 

 characters by which the species may be distinguished from others 

 are its delicate habit, somewhat sparse wide -spreading branches, 

 and short branchlets, which also diverge widely from the branches 

 from which they spring. 



hoc. Lower Arenig, Eoad Uchaf, Ramsey Island, 



Ptilograptus Hicksii, Hopk., sp. nov. PI. XXXYI. figs, la & 1 b. 



Brit. Assoc. Eeport for 1872. 



Slender, tripinnate; stem slightly waved, thicker than the branches; 

 primary branches, alternate, diverging from the main stem at 

 an angle of from 35° to 40°, and occasionally giving off secon- 

 dary branches, which form a very slight angle (about 15°) with 

 the primary ones, the secondary branches again giving off 

 slender branchlets in a similar manner ; hydrothecse about 40 

 to the inch, narrowly cup -shaped in form, and with minute 

 circular apertures. 



In its single, strong central stem, giving off from either side more 

 slender plumose branches, the branchlets of which soon become 

 parallel and densely crowded, this species differs much from any 

 before described, more nearly approaching an undescribed form from 

 the Ludlow rocks of Herefordshire than any Arenig species. 



The specimen figured was the first Graptolite found in the Arenig 

 rocks of Eamsey Island, being exposed by Mr. Hicks on breaking 

 open a piece of shale picked up almost immediately on landing at 

 the spot from which all our specimens from the Lower Arenig rocks 

 of this island have been obtained. The specific name given to it is 

 therefore peculiarly appropriate. 



Loc. Lower Arenig, Eoad Uchaf, Eamsey Island. 



