part 4] UPPElt ORDOTICTl^ OF THE BERWTX HILLS. 50-J 



angle with the anterior portion, from which point it runs in a 

 falling curve to the rounded genal angle. 



The four complete specimens each have twelve thoracic seg- 

 ments. The axis is broad and arched, joining the pleura? at about 

 100° ; the axial half of the pleura lies horizontal, while the 

 marginal half is sharply bent down to within 15" of the vertical. 



The outline of the pygidium is that of a bent bow (with cord 

 taut), the margins of the pleural portions being almost straight 

 lines. The axis is well denned, with usually four well-marked 

 rings and a large, broad, somewhat flat, posterior segment. The 

 pleural portions are well defined. Viewed from behind, the 

 pygidium shows a marked arching of the border towards the axis. 



The hypostome is of the normal Galymene type, so far as could 

 be judged from an imperfect specimen preserved in place in a 

 glabella. 



The dimensions of the holotype, in millimetres, are as follows : — 



Total length 21 Greatest width 17 



Head-shield; length 7 Width (at the genal angles) . 17 



Thorax; length 9'5 Width (anterior segment) .. . 15'5 



Pygidium; length 4-5 Width 10 



The holotype is preserved in the Museum of Practical Geology, 

 Jermyn Street, London, under the registration-number 31742-48. 



Belated forms. — This species has much in common with 

 Galymene planimetry inata Beed ( = Senaria of Salter in part). 

 This is indicated by the shape of the frontal margin and the 

 relatively great width of the glabella. It is easily distinguished 

 from C. planimarginata by the squareness of the glabella, and by 

 the almost equal and small size of the 2nd and 3rd glabellar 

 lobes ; the glabella is also more inflated in the new species. 

 Another form that appears to be related is Galymene caraciaci, 

 which usually comes in the highest Caradocian. G. caraciaci, 

 however, has a much narrower glabella and more graded glabellar 

 lobes. A specimen from the lowest Ashgillian of this district 

 appears to be intermediate between G. caraciaci and C. quadrata. 



Horizon. — Galymene quadrata has been found in the Ash- 

 gillian in the higher beds with Pliillipsinella 'parabola, and is 

 extremely abundant in the sandy mudstones of the higher part of 

 the Ashgillian in the South- Western Berwyns, where it has been 

 taken as an index-fossil for a group of strata. Among the 

 specimens found are four full-grown and three young complete 

 individuals, together with numerous isolated head-shields. 



LlCHAS getkei Etheridge & Nicholson, var. (PI. XXVI, fig. 3.) 



A sirigle example of a minute pygidium belonging to a Liclias 

 of the group of L. geihei was obtained from the lower part of the 

 Galymene-qaadrata Beds at cA on Craig-fawr (see fig. 3, p. 496). 

 The pygidium is subquadrilateral in outline, flat, with a well-raised 

 axis extending over half the length of the pj'gidium, ending 

 bluntlv, but continued as a narrow post-axial ridge to the median 



2m2 



