V4 



SILURIAN TRILOBITES. 



axe convexo, angusto, latitudine pleura dimidium haitd efficiente ; pleuris latis plants 

 punctato-sulcatis, apicibus acutis lente decurvis, secundo et tertio sese conniventibus. Cauda 

 lata, axe brevi turbinato A-annulato, annulo terminali trigono apicem emarginatum attin- 

 gente ; pleuris Q,primum rectis (duobus primis semisulcatis) dein arcuatis, apicibus retrorsis 

 foliaceis ovatis subaqualibus. 



I cannot do better than extract Prof. M' Coy's excellent description from the work 

 above quoted, and I think he is fully justified in placing this Lower Silurian form in the 

 subgenus Eccoptochile. It is, indeed, a near ally of Cheirurus claviger, Beyrich, from 

 which, however, its rectangular, not ovate, shape, and broad transverse flattened tail easily 

 distinguish it. 



"Cephalic shield nearly semicircular; glabella slightly clavate, smooth, with three seg- 

 mental furrows on each side; the posterior pair longest, turning backwards and inwards nearly 

 to the neck-furrow, enclosing a triangular space on each side longer than w T ide, the width 

 rather less than that of the undivided portion of the glabella beneath their bases, the two 

 anterior pair of furrows shorter ; cheeks broad, gently convex, closely and coarsely pitted ; 

 neck-segment thick, smooth ; eye-line extending with a slight curve to the margin in front 

 of the angles ; axal lobe very convex, narrow, slightly tapering, nearly parallel-sided, 

 smooth, of twelve segments ; three similar rings belong to the pygidium, a fourth terminal 

 one being obtusely trigonal; the side-lobes are flattened, and more than double the width 

 of the axal lobe ; pleurae nearly straight, narrow, and, for the greater part of their length, 

 flattened, and having a broad, nearly mesial, pleural sulcus, deeply punctured like the 

 cheeks, dividing each into two parts ; the posterior largest, and forming a thick, smooth 

 rounded ridge in the distal third of its length, bent down and a little backwards, swelling 

 to a thick, narrow ridge in the middle, the sides and the extremity expanding into abroad, 

 thin, foliaceous appendage ; the pygidium terminates in six broad, ovate, leaf-like, semi- 

 membranous flaps. Length of thorax and pygidium two inches two lines, width two 

 inches three lines ; width of axal lobe six lines. 



" This magnificent Trilobite can only be confounded with the Eccoptochile clavigera, 

 Beyrich, from which it is distinguished by the much greater width of the lateral lobes of 

 the thorax, and the thin, flat, leaf-like appendages of the pygidium, which in that species 

 resemble thick, pear-shaped clubs." 



Localitg. Llandeilo flags, two miles north of Builth, Radnorshire (Woodwardian 

 Mus.). Also Abereiddy Bay, Cardiganshire (Mr. H. Hicks). 



Ch. (Eccoptochile) Frederici, n. sp. PI. V, figs. 18 — 21. 



Cheirurus Frederici, Salter, in Mem. Geol. Surv., vol. 5, (ined.), pi. viii, fig. 1 — 3. 



Ch. {Eccoptochile) triuncialis et ultra, capite transverso, longispinoso. Glabella 

 oblonga parallela sen an/ice angustior, granulosa, sulcis distinctis abbreviatis obliquis quasi 



