384 F. R. Cowper Reed — Trilohites from Haverfordwest. 



its middle, and then scarcely at all to end with a blunt (?) 

 extremity just within the margin ; it is completely annulated to its 

 tip and shows 11-12 strong rings. The lateral lobes consist of 

 8 pairs of pleuras, of which the first seven are prominent, gently 

 curved, and separated by deep interpleural furrows, and each is 

 marked by a weak pleural furrow. The plenrte and furrows die 

 out before reaching the rounded margin, but there is no independent 

 border or marginal furrow to the pygidium. The whole surface of 

 the head, thorax, and pygidium is ornamented with granulations, and 

 there are also a few large tubercles on the frontal lobe of the glabella. 



Dimensions. mm. 



Leno'th of whole ti'ilobite 82*0 



Length of head ... ... ... ... ... 27*0 



Width of head (about) 56-0 



Length of thorax 33-0 



Length of pygidium (without spine) ... ... 22 '0 



Width of pygidium (about) 33-0 



Affinities. — Tliis species clearly belongs to the early group of 

 Dalmanites of Barrande, of which D. socialis is the type. Our 

 specimen is closely comparable with the variety of this species 

 termed procEva.^ In the characters of the head, so far as it is 

 preserved, there seems to be no difference ; the pygidium, except 

 in the shape of the axis, is identical, and the ornamentation is 

 quite similar. The species recently described by the autlior as 

 VJi. (Dalmanites) Robertsi- differs by the narrower and more elongate 

 glabella, by the shape and fewer segments of the p3'gidial axis, and 

 especially by the absence of the terminal spine of the pygidium. 



Pit. (Dahn.) appendiculatiis, Salter,^ has a somewhat similar glabella, 

 but the pygidium is more elongate and tapers to the mucronate 

 extremity ; the axis tapers regularly, and has fewer rings and an 

 appendix ; the ribs on the lateral lobes are falcate and undulate 

 the margin. 



Phacops (Dalm.\nites) aff. incertus, Deslongchamps. 

 (PI. XII, Fig. 4.) 

 There are several pygidia from tlie Slade Beds of the quarry 

 at Upper Slade, Haverfordwest, which seem to indicate a new 

 species of Phacops, the description of which may be given as 

 follows : — Pygidium broadly subtriangular, bluntly pointed behind ; 

 surrounded by narrow, depressed, concave, smooth border, not 

 mucronate, but slightly elevated and upturned behind axis. Axis 

 conical, tapering rather rapidly at first and then more slowly to 

 blunt apex, not reaching posterior margin ; extending about four- 

 fifths the length of the pygidium, and with a width at front end 

 a little more than a quarter that of pygidium ; gently convex, 

 annulated for whole length with about 12 or more rings, but only 

 the first 9 or 10 are distinct. Lateral lobes gently convex, each 

 consisting of a half pleura at front end followed by six simple, 



1 Barrande : Svst. Silur. Boheme, vol. i, p. 5 ')2, pi. xxi, fis'. 32. 



2 Heed: GeolI Mag.. Dec. Y, Vol. I, p. 106, PI. V. 



' Salter: Men. Brit. Trilob., p. 46, pl. iv, figs. 11, 12. 



