20 DEVONIAN TRILOBITES. 



that the axis looks nearly as wide as the pleurae. It is not in reality nearly so broad. 



The surface is coarsely granulated, as is that of the tail, when the crust is preserved. 



There is a perfect body," with eleven rings, in Mr. Vicary's cabinet, of which a 

 woodcut is here given. The axis is convex, seini-cylindric, tuber- 

 cular, very slightly nodular on the sides, and little more than half 

 as broad as the pleurae. These are very convex, and as steeply 

 bent down as in Calymene ; the fulcrum is placed at about one 

 third out, and as far from the axis in the hinder as the front rings. 

 The pleural groove is not very deep, and does not reach the long 

 facets. The ends of the pleurae are recurved and rounded. 



Tail in our specimens (figs. 14, 15,) wide, more than semicir- 

 cular, arched in front, and very convex, with the axis quite elevated, 

 and separated by broad furrows from the convex limb. A few 



Body and tail of Phaeops Mi- tubercles show on the ribs of the axis. It projects in front, 



frons ; Newton Bushell. 



slowly tapers to a rounded end at one sixth from the margin, 

 and is strongly annulated by seven or eight rings (ten in some German specimens) 

 while the convex sides slope quickly down, and have five or six strong ribs, straight, or 

 but little curved, and all but reaching the indistinct margin. There is no flat border. 

 The axis varies in breadth, but is never so much as one third the whole width, usually 

 one fourth. Incurved under margin very convex. 



Localities. — Lower Devonian. Hope and Barton, South Devon ; near Liskeard and 

 Totnes, in slates with Pleurodictymn problematicum. Upper Devonian (Pether- 

 win Group) ? Newton Bushell. Uppermost Devonian (Barnstaple Group). 

 Croyde, Barnstaple, and the neighbourhood ; Brushford, Pilton, &c, abundant ; 

 Yealm Bridge, north of Launceston (Pattison and Salter). 

 Foreign localities. — Rhenish Prussia, Belgium, France, Russia, {P. bufo takes its place 

 in North America) ; also the Andes, South America (Mus. Geol. Soc). 



Far. PI. I, fig. 16. 



I figure as a variety the wide pygidium found at Newton Bushell, which differs from 

 the ordinary forms of P. latifrons, by the narrower proportion of its more depressed axis 

 to the sides, — little more than one fourth, and in having the six side ribs more direct than 

 usual. It can only be a variety, but the aspect is different to that of the common form. 



Locality. — Upper Devonian.* Newton Bushell. 



* I consider the upper quarries of Newton Bushell as the equivalent of the Petherwin beds. This 

 subject requires minute examination, and will be determined chiefly by the labours of local geologists. 

 The upper limestones are clearly not of the same age as the great Plymouth limestone, but nevertheless, 

 they contain a good many of its fossils. 



