F. R. Cowper Reed — Trilohites from Saverfordwest. 385 



slightly curved pleura?, ending abruptly at concave border, and not 

 corresponding to the axial segments. Each pleura has a short 

 oblique furrow on its outer half. Interpleural furrows distinct 

 and of uniform strength for their whole length. Axial furrows 

 moderately sti-ong. 

 Dimensions, 



mm. 



Length of pygiclium 9*0 



Width 15-0 



Width of axis at front end 4-5 



Affinities. — This species in its shape and number of axial rings 

 and pleurae recalls Pli. appendiculatiis, Salter,^ but the pleurse in the 

 latter are deeply furrowed along their whole length and undulate 

 the margin. In Fh. Weaveri, Salter,^ the segments are more 

 numerous, though the contour and proportions of the pygidium are 

 not dissimilar. Ph. iiicertus, Deslongchamps, as recorded by Salter^ 

 from the Budleigh Salterton pebbles, has a pygidium almost identical, 

 and apparently it differs only in the possession of a more produced 

 and mucronate posterior end. The Slade form is undoubtedly more 

 closely allied to it than to any other. Salter (op. cit.) correctly 

 recognised that PA. incertus belonged to the group characterised 

 by B. socialis in Bohemia, and it is difficult therefore to see why 

 he ascribed it in the same work to the subgenus Acaste. 



Phagops (Chasmops) conicophthalmus, Boeck. (PI. XII, Fig. 1.) 



No member of the subgenus Chasmops appears to have been so far 

 described or recorded from the Haverfordwest district. Mr. Turnbull's 

 collection, however, contains two examples, one consisting of a fine 

 head from the Slade Beds of Upper Slade, which may be confidently 

 referred to the British form termed Chasmops con\j.c]ophthalmus 

 (Boeck) by Salter and others, though it is doubtful if it is really 

 identical with Boeck's species. The Slade specimen consists of a cast 

 and external impression, the latter of which shows the surface- 

 oharacters fairly well. In the shape and proportions of the glabella 

 and of the frontal lobe. ' cat's ear ' latei'al lobes, and third lateral 

 lobes, it is identical with Salter's figured specimen [op. cit., pi. iv, 

 fig. 25) in the Sedgwick Museum ; there is likewise to be noticed 

 the practical absence of the second lateral lobes, which are in most 

 species represented by small nodules; the convexity of the cheeks, 

 position and size of the eyes, and deep furrow round their base also 

 agree, but in our Slade specimen the eye is well preserved and 

 shows the lenses, which are arranged in about 25 rows, with a total 

 number of about 150 lenses in all. The eye-lobe is elevated, 

 prominent, and almost angulated, as Angelin's* figure shows, and the 

 genal angles are similarly jDroduced into long, broad, flattened spines, 

 steeply inclined to the general plane of the head-shield and extending 



1 Salter: Mon. Brit. Trilob., p. 46, pi. iv, fig. 12. 



^ Ibid., p. 57, pi. iv, fig. 7. 



3 Ibid., p. 30, pi. i, figs. 27, 28. 



* Angelin: Pal. Scand., p. 9, pi. vii, figs. 5, 6. 



