Palceosoic Fossils. 397 



Under reflexed surface rounded at the side-margins which are 

 slightly raised ; inner margin with a central triangular process 

 bent downwards. Surface of glabella finely granulated ; cheeks 

 smooth. 



Bodj' elongated, axis elevated and rounded, narrow, with no 

 indication of separation into thorax and pygidium. 



In the most complete specimen I count 13 segments. Sides 

 flat on eithet- side of the axis, then strongly bent downwards ; 

 ends of pleurae turned forwards with apparently a backwardly 

 directed spine. 



Remarks. — The coiled up thorax and tail figured by Salter, 

 PI. XXV., fig. 9, seems generally to agree with the thorax of this 

 species, but the Albany Museum specimens are too indistinct to 

 show the ornamentation of Salter's type if it had been once there. 

 The margin of the head being turned forwards, the pleurae have 

 to take on the same curve, and hence all the forms with this shape 

 of head, P. caffet\ P. caUitHs and P. gydowi^ would have bodies 

 indistinguishable one from the other as far as the forward curvature 

 of the pleurae is concerned, but the heads are quite distinct. I do 

 not therefore think Lake is justified in definitely claiming the 

 original of fig. 9 of Salter as belonging to his new species P. ocel 

 Ins. 



I have named the species after the Gydow, a steep pass lead- 

 ing from the Warm to the Cold Bokkevelds, Ceres, in the road 

 cuttings of which so many fossils have been obtained. 



Dimensions : Head. Length, 1.9 cm. Breadth, 2.4 cm. 

 Width ot glabella at base. LI cm., in front, 1.3 cm. Length of 

 glabella from neck furrow to front suture, 1.7 cm. ; from neck 

 furrow to base of first axial furrow, 0.7 cm. Width between eyes 

 (inner margin of facets), L<S cm. Body (No. 26). Total length of 

 head and body, 4..S cm. Length of l)ody (13 rings), 3.2 cm. 

 Width of axis, 0.9 cm. Width of wliole thorax, 2.1 cm. 



Cat. No. 25. Cat. No. 26. Type for body. Cat. No. 28. Type 

 foi- head. Locality, Gydow Pass, Ceres. Donor : Mr. A. G. 

 Bain. 



