﻿110 



BRITISH PALEOZOIC PHYLLOCARIDA. 



10. Aptychopsis subquadrata, sp. nov. Plate XV, fig. 20. 



Mounted on the same tablet, and presumedly from the same locality as 

 A. angulata (infra, PI. XV, fig. 19), but in a different matrix, is a slightly convex 

 cast of a suborbicular, or apparently subquadrate shield, with a relatively 

 long dorsal suture and a short notch ; and somewhat squeezed laterally. It 

 is in a brown, fine-grained sandy mudstone, full of hollow impressions of 

 minute fossils (Encrinital, &c). Concentric lines, indicated on the cast, are 

 rather broad and irregular. This differs markedly from fig. 19, and indeed from 

 any other form we have met with. We must therefore regard it as a new 

 species, and we propose to call it subquadrata. 



Measurements: | , 7 mm.; — , 5 mm. ; A, 3 mm. at 45°; 4 mm.; I, 

 3 (?) mm. ; V, 90°. Proportion, width and length equal. 



From the Lower (?) Silurian ; Cloncannon, Tipperary, Ireland. Mus. Geol. 

 Survey, Ireland. 



11. Aptychopsis angulata (Baily, 1860). Plate XV, fig. 19, and figs. 13 ? and 17 ?. 



Cucullella angulata, Baily. Explan. Sheet 135, Geol. Surv. Ireland, 1860, 



p. 13, fig. 4 (woodcut). 

 Aptychopsis glabra (?), T. It. J. and H. W. Beport Brit. Assoc. for 1884 



(1885), p. 91. 



This somewhat convex specimen and its hollow counterpart occur in the 

 bed-plane of a thin, brownish, hard, fine-grained sandy mudstone from Tipperary, 

 Ireland. It was figured as Cucullella angulata by the late W. H. Baily in the 

 ' Explan. Geol. Survey Ireland,' Sheet 135, 1860, as noticed by us in the ' Report 

 Brit. Assoc. for 1884 ' (1885), p. 91. The valves are represented by brown stains. 

 The concentrics are distinct, rather numerous, and irregular in strength. 



The outline of the complete carapace seems to have been a somewhat oblate 

 circle, that is, widened transversely. It is not nearly so truly discoidal as A. 

 glabra or A. Wilsoni, from which its oblateness, resulting from greater trans- 

 verse width, separates it. 



Measurements: | , 7 mm.; — , 7 mm.; _\, 6 mm. at 40°; v _ <9 9 mm.; I, 

 5 (?) mm.; V, 100°. The width of the whole carapace to its length was pro- 

 bably as 14 to 12. 



From the Lower (?) Silurian beds at Cloncannon, County Tipperary, Ireland. 

 Mus. Geol. Survey Ireland. 



