F. B. Cowper Reed — Trilohites, Haverfordwest. 99 



Family ACIDASPIDtE. 

 AciDASPis (Ceratocephala) Turnbulli, sp. nov. 

 (PI. IV, Figs. 4-7.) 



There are several specimens in the Sedgwick Museum of a species 

 of Acidaspis from the Sholeshook Limestone of the Haverfordwest 

 district, which, though imperfect, afford sufficient evidence to recognise 

 in them a new species. In one example the entire individual is 

 preserved with the exception of about half the thorax and pygidium. 

 The head-shield is not complete and is somewhat crushed, but with 

 the aid of another specimen exhibiting some of the missing features 

 more perfectly, a fairly full description can be given. 



Description. — General form broadly ovate. Head-shield large, 

 semicircular, moderately convex. Glabella oval or subcylindrical ; 

 median lobe convex, cylindrical, nearly parallel-sided, slightly 

 expanded at front end so as to overhang the lateral lobes. Two 

 pairs of lateral lobes present; the anterior pair small, elongate, 

 obliquely oval ; the posterior pair about twice the length of the 

 anterior pair, narrow, elongate, pointed anteriorly, extending about 

 half the length of the glabella. First lateral furrows strong, curving 

 at first inwards and then running parallel backwards to the occipital 

 furrows, thus completely separating median from lateral lobes of 

 glabella. Second lateral furrows weak, oblique. Axial furrows 

 arched gently outwards, increasing in depth posteriorly. Occipital 

 furrow distinct, broad. Occipital ring broad, prominent, rounded, 

 furnished with large median tubercle and pair of low, obscurely marked 

 transverse occipital lobes ; margin of ring provided with a pair of short, 

 stout, subparallel spines. Fixed cheeks swollen, curved, elongated. 

 Ocular ridge narrow, rounded. Surface of head-shield tuberculate, 

 with a few scattered tubercles of larger size. (PI. IV, Fig. 5.) 



Thorax of nine segments ; about 1^ times the length of head-shield. 

 Axis narrow, strongly convex, prominent ; axial rings furnished with 

 distinct lateral nodular swellings. Pleurse straight, horizontally ex- 

 tended at right angles to axis, each bearing a submedian broad elevated 

 ridge with a narrow anterior border separated from it by a broad 

 but shallow furrow, and a narrow posterior marginal band ; ridge of 

 pleurae bears two prominent tubercles regularly placed at the same 

 distance from the axis all down the thorax ; extremities of pleuraa 

 produced into two spines, an anterior short one and a posterior longer 

 curved one with a tubercle at its base. (Fig. 6.) Pygidium (imperfectly 

 known) broadly semicircular; axis (not well preserved) convex, 

 prominent; lateral lobes flat, horizontally extended, with margin 

 furnished with five or six pairs of long, slightly curved spines of 

 equal size (the points are broken off in the specimen) ; surface of 

 lateral lobes marked by three subparallel rounded pleural ridges, 

 the middle one being the largest ; the first ridge runs to the base 

 of the third marginal spine, the middle one from the first axial ring 

 to the base of the fourth, and the posterior and faintest one to the 

 base of the fifth. (Fig. 7.) 



