CKRATIOCARIS STYGIA. 41 



four segments, 30 mm., and in each case two short ensiform stylets attached 

 (style wanting). 



PI. XI, fig. 3. Mus. Pract. Geol., x T V, x (' Catal. Camb. Sil. Foss.,' 1878, p. 142, 

 G. robustus). Lower Ludlow ; Leintwardine. In hard olive-green shale, finely 

 micaceous, not calcareous. 



This seems to belong to G. stygia. It shows two segments and appendages, 

 pressed sideways. Style, 50 mm. ; one stylet present, broad and ensiform, 23 mm. 

 long. The lattice-pattern ornaments the segments and head of the telson, which 

 latter is much crushed. 



M. P. G. x yg-a, -£gb, 2^ J, Logan Water, Lesmahago. Segments with oblique 

 strise (one ultimate segment has straight strise), not well preserved. Probably 

 G. stygia, as named in the ' Catal.,' 1878, p. 142. 



PI. X, fig. 7 (Cambridge Mus. &/35). An internal cast of a convex valve, 

 retaining a very thin film of the test. The antero-dorsal angle has been damaged. 

 This valve, in " Ludlow " rock (grey, micaceous, partly calcareous sandstone) from 

 Benson Knot, Kendal, belongs probably to C. stygia, 1 or a variety of that species, 

 if it be not a male individual, having (like PI. XII, fig. 2) less ventral depth than 

 usual among the many specimens from Lesmahago. The surface has parallel, 

 longitudinal strise ; very delicate in the dorsal region, coarser below the middle, 

 where they curve with the ventral margin, and here and there some die away. 



Cambridge Mus. b/6 is a large hollow cast of a similar valve, imperfect. 

 Upper layer of the stone with the cast not calcareous ; lower part calcareous. 



PL XI, fig. 1 (Cambr. Mus. &/36) is a caudal extremity, found also at Benson 

 Knot, which would apparently suit such valves as PI. X, fig. 7, and is not 

 distinct from G. stygia, except that the telson has a bulbous or rounded head. As 

 this is probably a specific character, we must not refer the associated valves 

 (PL X, fig. 7) to G. stygia without some doubt. It is possible, however, that the 

 latter species may have had such a telson-head, but that pressure and decomposi- 

 tion have generally destroyed all trace of it in the fossils. 



A fine large specimen of this narrow variety of G. stygia (?), with a round- 

 headed telson, is in the Museum of the Geological Survey of Scotland (M. 447), 

 Edinburgh, from Baglinside Burn, River Nethan, 4^ miles south-west of 

 Lesmahago. 



The specimen A, Oxford Museum (Grindrod Collection), PL XI, fig. 7, 

 consists of the penultimate (11 mm.), and ultimate (20 mm.) segments, both finely 

 lattice-marked, together with a broad style (45) and corresponding stylet (22 mm.), 

 of what seems to be too large for G. robusta, but not long enough for G. longa. 

 These caudal spines are strong, broad, and ensiform, the style is fluted ; the stylet 

 flat, except its marginal rims. The two segments are neatly ornamented with 

 1 ' Fourth Kenort Foss. Phyll.,' 1886, p. 232, and 'Geol. Mag.,' 1886, p. 459. 



f> 



