﻿DISCINOCARIS GIGAS. 



123 



At Cambridge two fragments of the same large kind of carapace (fig. 2) are in 

 the University Museum, from the Coniston mudstone of Skelgill Beck, Ambleside. 

 Collected by Mr. J. E. Marr, F.R.S. 



The late Mr. James Dairon, F.G.S., of Glasgow, kindly sent us a sketch 

 (fig. 3) of a fine specimen of this Discinocaris, found by Mr. William Brown (of 

 Birkhill, Dumfriesshire) in the graptolitic shales of Dobbs Linn, Moffat. It has 

 somewhat the outline of the bottom of a horse's hoof, boldly curved on one edge, 

 and broadly indented with a shallow triangle on the other. It has been much 

 more convex than it is now, being somewhat crushed, and radiately cracked 

 towards the curved margin. The figure measures 3 inches (73 centimetres) trans- 

 versely from one side of the curve to the other, and about 2 inches (5| centi- 

 metres) from the apex of the triangular indentation to the opposite edge. The 

 sides of the notch, about 25 mm. long, slope at 15°, and the angle of the notch is 

 150°. 



PI. XVII, fig. 1. An iridescent, pyritous film, on a bed-plane of black 

 graptolitic shale from Dobb's Linn, hard and finely micaceous, with ferruginous 

 joints. This is a left-hand posterior corner of a test like fig. 3, except that the 

 hinder border was straighter than in Mr. Dairon's sketch, reproduced as fig. 3 ; 

 and the concentric lines are more closely set towards the margin. Coll. Lap worth. 

 Brit. Mus. No. 59620. 



PI. XVII, fig. 2. A pyritous film of a crushed portion of the posterior corner 

 of the right side on black, graptolitic, finely micaceous, shale, hard, squeezed, 

 thick, and jointed. Graptolitic mudstone, A. Z. ; Skelgill Beck, at the lower 

 footbridge. Fig. 2 is taken from the convex counterpart of the split specimen. 

 Coll. Marr. Woodwardian Museum, Cambridge. 



PI. XVII, fig. 3. Copy of Mr. Dairon's sketch of a large unique specimen. 

 Evidently once subcorneal, but flattened by pressure. The measurements are 

 stated above. The dotted outline gives the probably correct shape of the test 

 without its nuchal piece. 



PI. XVII, fig. 4. An iridescent film, once pyritous, on the usual black 

 graptolitic shale of the Moffat series at Dobbs Linn. The figure is taken from 

 the convex counterpart. The straight edge is formed by a joint, whilst the 

 other or smooth convex edge, against which the parallel striae abut, may possibly 

 be a portion of the edge of the nuchal notch of a very large individual, the frag- 

 ment being 30 mm., and the whole length of such an edge on the notch of fig. 3 

 is only 25 mm., with the striae meeting it at a considerable angle instead of being 

 straight as in fig. 4. Coll. Lapworth. Brit. Mus. No. 59620. 



Tl. XVII, fig. 5. A greyish film, once pyritous, on the counterparts of thin 

 Moffat shale mentioned above at p. 122. May be regarded as body-segments 

 belonging to D. gigas. Coll. Lapworth. Brit. Mus. No. 59620. 



