PHACOPS. 3 



suddenly over the two front sides to the border, which it constantly overhangs, and 

 marked with two indistinct scars indicating frontal furrows. Basal lobe narrow, 

 distinct, arched and granulated centrally ; flat, smooth, and expanding laterally ; 

 separated from the front part of glabella by a furrow, deep on the sides, shallow 

 and curving in centre. Neck-furrow similar to the basal furrow but straighter. 

 Neck-lobe narrow, arched, smooth. Lateral processes straight, separated very 

 indistinctly from cheek by a slight furrow, and ornamented with a row of 

 tubercles. Cheeks oblique, receding, widely rounded at the latero-posterior corner. 

 Border wide, defined within by a slight concavity. Surface behind the eye 

 narrow, slightly swollen. Eye very large, occupying more than half the cheek, 

 semicircular, with straight sides almost, but not quite, as high as the glabella. 

 Lenses very large and convex, in eighteen perpendicular rows of from four to six 

 lenses each, between eighty and ninety in all. Lobe of the eye smooth, swollen, 

 connected with the basal lobe. Facial sutures obscure. 



Thorax with eleven segments. Axis narrow, much arched. Pleuras flat and 

 grooved at first, then bending suddenly down at the fulcrum where the groove 

 disappears ; extremities rounded. 



Tail wide. Axis narrow, convex, conical, reaching close to the hind border, 

 with nine segments divided by eight grooves, the posterior ones indistinct. Limb 

 separated from axis by strong concavities, convex, with eight segments vanishing 

 at the border. 



Size of Head. — 15 mm. long, 30 mm. wide, and 9 mm. deep. 



Size of Thorax and Tail. — Length, 32 mm. ; width, 22 mm. ; depth, 6 mm. 

 (about). 



Localities. — This handsome Trilobite is by no means uncommon at Lummaton. 

 I have obtained eight examples of the head from that locality. There is another 

 in the Battersby Collection in the Torquay Museum, and one in the Bristol 

 Museum. There are two specimens of the tail in the Woodwardian, and I have 

 three or four more, as well as one united to the thorax. There is a specimen of 

 the head in Mr. Vicary's collection from Wolborough, and another, in Mr. 

 Pengelly's collection, which was figured by Salter. 



Remarks. — This species is widely different from Phacops latifrons, (Bronn), 1 

 and from Ph. Schlotheimi (Bronn), 2 but it comes very much nearer to Ph. granulatus 

 (Miinst.), 3 with which, in fact, it seems to have been united by some authors. A 

 careful examination, however, has convinced Mr. Roberts, Mr. Marr, and myself 

 that it is really to be regarded as distinct. Judging from Minister's figures there 

 is at first sight small reason for doubting its identity, but, in his description, he 



1 1825, Bronn, in Leonhard's ' Zeitsch.' (afterwards ' Jahrb.'), pt. 1, p. 318, pi. ii, figs. I, 2, 3. 



2 Ibid., p. 319, pi. ii, figs. 5, 6, 7, 8. 



3 1840, Miinster, ' Beitrage,' pt. 3, p. 36, pi. v, fig. 3. 



