12 



BRITISH FOSSILS. 



We have seen the eyes of this species, and they are reticulated as in other species of 

 Phacops. But from their greatly curved shape they are generally broken off, and 

 this has led Professor M'Coy to the establishment of his genus Chasmops, which had 

 better be expunged, as this group is so closely connected with the ordinary Phacops 

 by means of such species as P. Brongniarti and P. Jukesii. 



Localities In Bala Limestone ; Llansaintffraid Glyn Ceiriog, south of Llangollen ; 



Alt-yr- Anker, Meifod, North Wales [M'Coy], Welshpool [Sil. Syst] ; Llanfyllin, 

 Montgomeryshire ; Llanbedrog, Carnarvonshire [Survey Coll.] ; Applethwaite 

 Common and Coniston, Westmoreland [M'Coy]. Caradoc Sandstone ; Cheney 

 Longville, Shropshire [Sil. Syst., figured specimen] ; Acton Scott, &c., abundant. 



Section Odontochile (Dalmannia), Decade 11. Pl. 1. 



Additional British Species, 



P. mucronaius, Brongn. sp. Entomostrac. caudatus, Wahl. Nov. Act. Soc. Tips., v. 8. t. 2. 

 £ 2. Asaphus mucr. Brongn., Cr. Eoss. t. 3. f. 9. Dalraan, Pal., t. 2. f. 3 a b. Phacops, 

 Emmrich (1839), Diss. 24. N. Jahrb. 1845. Burmeister, ed. 1. p. 113., anded. 2. (1846), 

 p. 95. (excl. syn. Murch. " Sil. Syst.") Angelin, Pal. Suecica (1852), t. 8. f, 1. 



P. triuncialis et supra ; glabella convexd, antice parum dilatata, utrinque lobis tribus 

 subcequalibus transversis, sulcis longis satisque profundis sese separatis ; caiidd late tri- 

 angulari acuio, axi subconvexo limbum planum hand cequante, in 9-12 annulos et appendicem 

 trigonalem diviso, appendice in apicem caudce brevi-mucronatum percurrente ; lateribus costis 

 7 planis, sulcis angustis acutis valde curvatis et cum tot lineis intermediis profundioribus ad 

 apices confusis ; margine angusto nec distincto. 



Portions of the head and perfect caudal shields of this rare species have been found 

 in a stratum over the bed of volcanic ash at Pen-y-Rhiw, west of Bala, where it is 

 to be hoped other collectors may obtain fresh specimens. The head is not complete 

 enough to give the diagnosis. Our Bala specimens, as weU as those from Sweden 

 in Sir R. I. Murchison's cabinet, have but 9 rings and a triangular terminal portion 

 to the axis of the tail, but in a specimen from Haverfordwest part of this terlninal 

 portion is annulated, and there are 12 rings. The lateral ribs are much arched 

 at their ends, and strongly duplicate, of double furrows, each pair uniting at their 

 tips in a broad depression. The apex is recurved ; the mucro varies in length. 

 Localities. — Pen-y -Rhiw, west of Bala [Survey Coll.] ; Haverfordwest, Pembrokeshire 

 [Mrs. Day's cabinet] ; in Llandeilo flags. 

 P. amphora, n. sp, 



P. Cauda magna biunciali elongatd, convexissimd, fere semicylindrica ; sulcis axalibus fere 

 obsoletis ; axi lato nec eminenti, marginem caudce haud attingente, in annulos sexdecim sub- 

 pianos diviso, apice obtuso ; lateribus valde curvatis dejlexis, costis 14-15 planis, sulcis 

 acutis separantibus, — costd qudque lined mediand Icevi elevatd (sub cortice impressd !) ; 

 margine angusto injiexo, apice obtuso (emarginato ?). 



Very like in general form to P. truncato-caudatus, Portl., from which it is at once 

 distinguished by its convex form (almost like that of a half cask or barrel), and the 

 axis not at all distinct from the sides — the axal furrow being almost obsolete ; this 

 latter character is very unusual in Phacops. Along the middle of each of the 

 flattened side ribs a narrow and but slightly elevated ridge runs the whole length ; 

 on the internal cast this is represented by a depressed line of connected dots. 

 Something similar, but less distinct, occurs in the allied species above quoted. 

 Locality — Grug Quarry, near Llandeilo [Survey Coll.] ; one fine specimen was 

 presented by Mr. Williams, of that place. In Llandeilo flags. 



J. W. Salter. 



August^ 1853. 



