1866.] SALTEB NEW SPECIES OE TRILOBITES. 487 



quoted above), but neatly impressed and nearly reaching to the 

 centre. The upper lateral lobes are triangular, the middle transverse 

 and oval ; the basal are linear, transverse, and nodose at the ends. 

 The neck-furrow is strong, and the neck-segment not broader than 

 the basal lobes. 



The cheeks (imperfect) appear triangular, and are gently convex for 

 a large space before reaching the very large curved eyes. These have 

 the eye-lobe linear and distinctly marked out ; and the lentiferous 

 surface, broad and much arched, reaches from the termination of the 

 upper pair of furrows very nearly to the neck-furrow, which is rather 

 broad and well defined. We do not yet know the free cheeks : they 

 were probably short and mucronate. 



The body-segments (seven are preserved in Professor Hark- 

 ness's specimen) have a rather broad depressed axis, the rays being 

 obscurely nodular at the ends. The axial furrows are slight, and the 

 pleurae are flat as far as the remote fulcrum, which is placed halfway 

 out. They are deeply, but not widely, grooved to the very end of 

 the obtuse tips. 



The pleurae are bent down from the fulcrum, but not strongly, 

 unless the specimens are both compressed vertically (I think not), 

 and a little recurved. 



Tail semicircular, convex only on the lateral lobes, which show 

 five straight long furrows directed a little backward, and as many 

 faint intervening ones. The axis is moderately broad, conical, and 

 rounded at the tip, which reaches nearly to the end of the tail. 



Locality. — Whiteside, three miles west of Braithwaite, Keswick. 



2. Agnosttjs Morei, Salter. Eigs. a & b. 



Ref. Decades Geol. Surv. xi. p. 7. pi. 1. f. 13, 1864. 



In the Decade I was only able to give a figure of the head of 

 this most characteristic species, obtained by Mr. Lightbody and my- 

 self from the blacklead-bearing shales west of the Stiperstones, 

 Shropshire. 



It is an excellent proof that we are right in referring the Skiddaw 

 slates to the verge of these old Shropshire beds ; so that the term 

 " Arenig or Skiddaw group " of Sedgwick is no longer a hypothetical 

 association, but indicates a definite horizon. 



The head (it is figured at a from the Decade just quoted) is sub- 

 quadrate in outline ; and the narrow bilobed and pointed glabella is 

 surrounded by a broad limb, deeply indented by numerous depressed 

 rays, interlined by shorter ones near the margin. 



The tail, now figured (h), shows exactly the same ornament : nume- 

 rous (10 or 11) deep long depressions radiating over the limb, not 

 even, but nodose in their character, and interlined by smaller ones 

 toward the margin. The outline is quadrate, the border narrow, 

 except where it is produced into the short spines on the hinder edge ; 

 and these occur nearly as far back as the posterior margin. The 

 axis is about half the length of the tail, broad, short, pyramidal above, 

 soon cylindrical, and much flattened, marked across by two pairs of 



VOL. XXII. PART I. 2 L 



