PHACOPS. 37 



P. {Chasmops vel Acaste) modicus, unciam lotus, granulosus, capile transverso fere quam 

 longq ter tatioro; glabella dilalatd, lobis omnibus distinctis. Glabella subconvexa, frontem 

 impendens, late triangulata, antice valde dilatata, nee cum margine connata, piostice 

 contracla, utrinque triloba ; lobo bascdi transverso linsari, secundo paidlo majore rotundato, 

 supremo mag no triangulate, frontali maximo transverso oculos imminente, cervicali elcvalo. 

 Sulci axillares profundi. Gence lata- marginal a, transversa — angulis rotundatis ?, sulco 

 cervicali forte exarato, lined faciali impressd. 



It may be doubtful if this species be not included in some of the varieties of 

 P. selerops, Dalman ; but it is clearly distinct from his typical form, as we know by 

 specimens in the cabinet of Sir R. I. Murchison. And it well deserves a name, being a 

 most characteristic form, which somewhat tends to connect the ordinary species of 

 Acaste with the more extravagantly lobed species of Chasmops. I scarcely know lo 

 which sub-genus it should be more properly referred, and place it first. We have only 

 two specimens. 



The head is above an inch wide, and scarcely more than one third its length : convex 

 and granulose, with coarse and fine grains equally all over. The glabella not convex, but 

 greatly dilated in front, and contracted behind to one fourth the width. The forehead- 

 lobe is widely transverse, and overhangs completely the triangular upper lobe, which in 

 its turn is imminent over the mid-lobe, and about twice its size. The middle lobe is, 

 however, wider than the narrow basal lobe, which is not reduced to a mere tubercle 

 on the sides, nor contracted to a much less width than the rather prominent 

 neck-lobe. 



The cheek, strongly margined in front, is of a narrow triangular shape, and is deeply 

 divided from the glabella. The eye, much curved, is opposite to and covers the space of 

 the two upper lobes, and is itself overhung by the upper lobe. 



The facial suture is deeply marked outside the eye ; it nearly bisects the cheek, and 

 runs parallel to the deep neck-furrow. 



A young specimen does not differ in any material respects from an older one. 



Zocalilg. Caradoc Rocks of Gelli grin, near Bala, North Wales. (Mus. P. 

 Geology.) 



P. (Chasmops) macrolra, Sjogren, PI. IV, figs. IS— 23. 



AsAPHTJS Powisii, Murchison. Silurian Syst., pi. 23, fig. 9 (head only), 183". 

 Dalmannia affinis, Salter. Memoirs Geo!. Survey, vol. ii, pt. 1, pi. v, fig. 5, 18-18. 

 Phacovs TKUNCATo-caud vrus, var. ft, affinis, /(/., in Decade Geol. Surv., No. 2, 



Art. 1, p. 7, 1849. 



