52 PEOCEEDIls^GS OF THE GEOLOGICAL SOCIETY. 



in a series of red and purple rocks sev^eral hundred feet lower; and 

 these will be described by-and-by*. The present communication 

 illustrates only some characteristic Trilobites from the grey beds at the 

 base of the " Menevian Group," and two forms from the black slate 

 series directly above these beds. 



Of these we only describe at present Paradoxides and ConocorypJie, 

 and complete these genera so far as they are yet known in the "Mene- 

 vian Group" proper. The several species in the genera Erinnys or 

 Hcuyes, Arionellus, and Agnostus, are still to be described. 



1. CoNocoEYPHE BUEO, Hicks, PI. II. fig. 8. Brit. Assoc. Eeport, 1865, 



p. 285. 



Of this well-defined species, only a few separate heads, and one 

 with six body-rings attached, have been found. It is much the 

 largest species of the genus yet found in the " Menevian Group," 

 being probably no less than 3 inches in length and 1| in breadth 

 across the head. The head is semicircular, tubercular all over, 

 strongly marginate, with the angles produced into short spines. The 

 glabella occupies nearly two-thirds the length of the head, is very 

 narrow forwards, parabolic and convex, and is indented by three dis- 

 tinct lateral furrows on each side, which run obliquely backwards 

 and reach about one-third of the distance across ; length about equal 

 to width at the base, centre ridged slightly, neck-furrow deep, well 

 defined, and arched somewhat upwards in the centre. Occipital ring 

 almost as convex as the hinder part of the glabella. Cheeks wider 

 than glabella, almost equally convex with it, and separated from it by 

 very deep dorsal furrows ; their posterior margin is narrow, bent for- 

 ward near the outer angles, and bears a strong tubercle on either side. 

 Eyes small and scarcely visible, placed very far from the glabella. 

 The facial sutures curve outwards above the eyes, and beneath them 

 are nearly marginal, just cutting off the spinous angles. The outer 

 border, which is narrow round the cheeks, becomes greatly exagge- 

 rated in front, and widens to a triangular tumid boss, the apex of 

 which reaches backwards almost to meet the anterior part of the gla- 

 bella; in consequence of this the marginal and dorsal furrows approxi- 

 mate each other, and become almost merged into one another at this 

 spot. This boss is at least a fourth of an inch wide opposite the apex 

 of the glabella, rises suddenly upwards from the marginal furrow, 

 and then slopes forwards gradually. The whole surface is granular, 

 with some larger tubercles. The thorax, of which six rings only 

 have been found attached, has a highly convex axis, about half as 

 wide as the pleurae with the attached spines; pleurae depressed, 

 grooved widely in the castf? and turned sharply backwards at the 



* It is perhaps advisable to mention what these are, leaving their description 

 till another time: — Anew genus, Plufoma, a Conocoryjjhe, a Paradoxides, a 

 Mlcrodiscus, Agnostus, Theca, Lingulella, and a new bivalved Crustacean. It 

 really does look as if the changes rung on tliese early forms were not so much 

 varied as we" descend lower in the geological scale. Hence we may hope to 

 reach some point beyond which the variations are zero. — J. W. S., Dec. 1868. 



t The shell is probably very thick, and the groove on the upper crust 

 would not be nearly so strong as in the cast. 



