172 



C. LAPW0ETH ON SOME NEW 



inch in transverse diameter, radiating from the centre with few and 

 remote bifurcations ; approximately parallel distally ; having 25 

 branches to the inch, connected by frequent capillary dissepi- 

 ments 12 or 13 to the inch. Calyclcs biserial, closely adpressed to 

 the polypary, 50 to the inch ; apertural margin acute, rarely spinose. 



The largest specimens obtained are distal fragments of the 

 polypary, about two inches in length ; and from the characteristics 

 presented by these fragments the foregoing diagnosis has been 

 drawn up. 



This form is undoubtedly new to British palaeontology. It may, 

 however, be proved in the future to be identical with some of the 

 imperfectly known American forms from the Clinton and Niagara 

 groups. 



Locality, Llandovery of Devil's Bridge, Aberystwyth. Dictyonema 

 venustum is a rare fossil in the Llandovery rocks, of the south of 

 Scotland, at Abbotsford, Winterhope, and Penwhapple Glen. 



2. Dictyonema delicattjltjm, sp. nov. Plate YIL figs. 2a, 2b. 



Polypary cyathiform ? probably three or four inches in transverse 

 diameter. Branches 40 to the inch, about of an inch in 

 width, distally parallel, connected by indistinct capillary dissepi- 

 ments 16 or 17 to the inch ; bifurcations ? Calycles biserial, 80 to 

 the inch ; aperture horizontal, devoid of ornament. 



The best example of this species collected is shown in the figure, 

 Plate YIL fig. 2a. The characters it presents show that it 

 belonged to a distinct species from that already described, from 

 which it differs mainly in the narrower and more closely-set 

 branches, and in the more numerous calycles and dissepiments. 



Horizon and Locality. Llandovery of Bryn y Carnau, Aberyst- 

 wyth. 



A single specimen has also been collected from the Pentamerus- 

 beds of Shalloch Porge, Girvan, South Scotland. 



3. Dictyonema coeetjgatellijm, sp. nov. Plate VII. figs. 3a, 3b. 



Polypary cyathiform, about one and a half inch in height. The 

 branches are nearly parallel, about yJ-jj of an inch in diameter, and 

 J- - of an inch apart, connected by fine transverse dissepiments at 

 regular distances of about of an inch, undulating in direction, the 

 edges being thrown alternately from side to side by the projection 

 of the outer margin of the calycles. Calycles 120 to the inch, 

 alternate, with gibbous outer margin, and deep rounded aperture 

 lying interior to the edge of the branch. 



The most striking feature of this elegant little species is formed 

 by the wrinkled or undulating outer edges of the branches, which 

 wave from side to side owing to the projection of the ventral 

 margin of the calycles. The slender branches divide more 

 frequently than is the case with the generality of species of 

 Dictyonema ; and the transverse dissepiments are stouter and appa- 

 rently polypiferous. 



The calycles have their apertural margin strongly introverted. 



