202 Prof. T. R. Jones and Dr. H. Woodward— 
cylindrical telson, or last abdominal segment. This has left a strong, 
black, shining film, bearing irregular chevron-like marks, with their 
angles pointing upwards. These have some resemblance to the 
ornamentation of the style of Phasganocaris pugio (Barrande), as 
figured by Novak in the Sitzsb. bohm. Gesell. Wissen. 1886, pias 
figs. 5, 7, 12, and 14; but the telson of that species has the leaf-like 
ornament present on some of the Ceratiocarides, and not the angular 
striation of the present form (fig. 8). 
The longest or middle spine is bulbous at the top, fitting into the 
end of the telson; and the two stylets appear to be articulated to 
the lateral angles, where the end of the telson widens out. The 
longitudinal striz (fig. 8b.), such as one of these two. lateral spines 
exhibits, may have characterized the others; and the central spine 
(style) seems to have been strongly ridged along its median line. 
As far as the materials serve, we think that fig. 8 may well be of 
the same genus and species as fig. 9 (C. insperata). 
Fig. 8a and b, two counterparts (natural size), black shining films, 
on hard dark-grey shale, of the Arenig series, from Llechwedd 
Deiliog quarry, about six miles HE. of Ffestiniog. 
Greatest length of specimen, 41mm. Length of the fragment of 
the last abdominal segment, 16mm. Greatest width of the last 
abdominal segment (at its distalend), 7mm. Least width (at the 
proximal end of the fragment), 4mm. Length of one stylet, 
225mm. Length of the other, not so well exposed, 21mm. 
Length of the style (middle spine), 26mm.; width at its head 
(proximal end), 4mm. 
The obscure appearances of other lateral spines, in fig. 8a, are 
quite adventitious, being due to the irregular surface of the shale, 
as seen more Clearly in fig. 8e. 
Fig. 9 is a careful illustration of the fossil described and figured 
by Salter, and preserved in the Woodwardian Museum at Cambridge. 
The trifid caudal appendage is clearly shown in the natural impres- 
sion; and two at least of the spines appear to have been ridged or 
fluted. The telson is obscurely indicated. 
Fig. 10. An impression or cast (natural size) in dark-grey hard 
shale from the Upper-Tremadoc series, at the railway-cutting above 
Penmorfa, Portmadoc. Collected by Mr. D. Humfrey. 
Middle spine (style), 28mm. long. Outside spines (stylets),. 
about 18mm. long. Width of the end of the telson, about 7mm. 
8. The subtrigonal, probably crustacean, test here figured came 
from the Upper Silurian beds at Church Hill, Leintwardine, near 
Ludlow, and is preserved in the Owens College Museum, Manchester. 
Length of the fossil, 53mm.; its greatest width, 23mm.; its 
least width, 10 mm. 
Taking the straight edge (a) as indicating a dorsal border at top, 
we see that each end of the fossil has a sloping edge,—one (b) much 
longer, and sloping at a lower angle (45°) than the short steep 
slope (c) at the other end (60°). This last turns rapidly to the 
2. ls 
