Xlll 



nisable on each face. The stylets are sulcate, their riblets or 

 costulae between the furrows varying in number up to sis. 

 Page 117, line 12 from top, insert The style has only a midrib ; the stylets have three or four 



costulae. At the end of tbe third paragraph add ; and this accords 

 with the disturbed (probably twisted) state of the abdominal segments 

 outside the carapace. 

 for XXIX read XXXI. 

 ,, after fig. 4 insert a, b, c, d. 



,, delete the icords between shows and part. 

 ,, delete impress of the. 



,, add For a more correct description of the magnified figure see below. 

 ,, delete the icords between shows and that. 



,, add PI. XXXI, figs. 4 a, b, c, d, being magnified figures of this specimen, 

 allow of a more correct description, thus : 

 Size. — Stylets possibly about 35 mm. long when perfect. 



Characters. — This specimen, magnified two diameters, shows the ventral aspect of a part of the 

 last abdominal segment and of the trifid appendage. Parts of the dorsal face of each stylet are shown 

 iu intaglio by the loss of the ventral moiety. A part of the head of the left-hand stylet has been 

 broken away, leaving an impression of its dorsal surface, shown by fig. 4 b. This figure (magnified 

 ten diameters) also shows the subsidiary oblique strife on the riblets of both faces, which are four on 

 tlie ventral and six on the dorsal face. 



The minute lateral striae trend upwards, i. e. backwards, on both faces, but are more delicate and 

 numerous on the riblets of the dorsal face. Marginal pittings, which were the bases of hairs, setae, 

 or spinules, are magnified in fig. 4 c, from the right-hand stylet. 



The ornament of chevron-like lines, with short, oblique, intermediate cross-lines is seen on a mag- 

 nified (30 diameters) part of the ultimate segments in fig. 4 d. 



The style is straight, coarsely fluted above and bayonet-shaped below ; the stylets are slightly 

 curved ; coarsely striate on the dorsal, and sulcate on the ventral face. 

 Page 151, line 22 from top, /or fig. 1 read fig. 1 a. 



„ ,, ,, 2 from bottom, add It retains part of the ventral fringe. There is the mark of a gastric 



tooth in its place ; and there are two separate teeth, obscured 

 ■with a shaly coating, in the slab. 

 ,, last line, /or Black calcareous shale read From the Cement-stone. 



152, line 22 from top, add In hard dark-coloured calcareous shale. 



153, first line, after 10 a, b, add c ; for 11 read 11a, b ; for 12 a, b, read 12 a—d. 

 ,, line 11 from top, read which we were at first inclined to refer. 

 „ between lines S and 9 from bottom, insert Dithyrocaris testudinea. — Mus. Geol. Surv. 



Scotland, Xo. 1, F. Y, and Xo. 8, F. y , counterpart.-^, not 

 figured. In hard, dark grey, non-calcareous shale, with 

 the tooth-mark strong, and a trifid obscure. One piece 

 marked Ardross, and the other Ardrosa Castle, Fife, 

 Lower Limestone Group. 

 ,, also insert D. testudinea, B. M., No. 16, not figured, is an imper- 



fect left valve, showing both the fringed ventral margin 

 and the dorsal crest (slightly separate), very much like 

 PI. XXVIII, fig. 1. 



