12 DEVONIAN FAUNA. 



rendered obscure by the presence of longitudinal markings giving with the transverse 

 furrows a very complicated pattern. The head is generally very wide, and the tail 

 small. The profusion of long fine spines on the borders, the ribs, the neck, and 

 other parts of the body, renders it a remarkably conspicuous genus. 



1. Acidaspis Robektsii, Whidborne. PL I, figs. 17, 17a. 



1889. Acidaspis Bobebtsii, Whidb. Geol. Mag., dec. 3, vol. vi, p. 29. 



Description. — Head-shield small, wide, rather flat. Glabella long, depressed, 

 almost quadrilateral, rather wider behind, reaching to the border in front, and 

 extending half as far again as the cheeks behind ; crossed by three straight, shallow 

 constrictions, apparently representing the frontal, ocular, and neck furrows, the 

 first of which is barely visible, and is close to the front margin. Immediately in 

 front of each of these constrictions, a pair of warts appear near the sides of the 

 glabella, which might have borne small spines. On each side of the rear of the 

 neck-lobe, two slender, flatly set spines, which are longer than the glabella, and in 

 the centre just in front of them a tubercle which apparently bore a spine set more 

 perpendicularly. Border raised, rather straight and oblique in the front part, 

 turning suddenly midway, and becoming almost concave just before the angle ; in 

 outline slightly sinking on each side. Cheeks irregularly convex, divided into two 

 nearly equal parts by a raised curved line, running from the front of glabella, and 

 terminated at the hind margin apparently by an elevated spine ; the part of the 

 cheek on each side of this being concave ; the part beyond it becoming a groove at 

 the angle, which seems also to have borne a spine ; and the part within it joined 

 to the glabella by three rounded processes sloping obliquely backwards to it, and 

 leaving deep pits between them. Hind margin of cheeks defined by the last of 

 these processes, assuming the shape of an inverted w. 



Size. — Length of glabella 12 mm., length of cheek 8 mm., width of head to 

 base of cheek-spine 20 mm. 



Locality. — A single specimen was found at Lummaton by Mr. Thomas Roberts, 

 F.Gr.S., and was presented by him to the Woodwardian Museum. 



Remarks. — Mr. Roberts' specimen is very far from perfect, and indeed, but for 

 the careful way in which he has developed it, would have been impossible to 

 identify. The outside edge of the border is gone, so that it gives no evidence 

 whether, like A. lacerata, it carried spines. There is no trace of the position of the 

 eye, but probably it was borne on the end of the long spine or stalk at the base of 

 the central line of the cheek, as in that species. The hind border of the cheek or 

 lateral process of the neck-lobe is also invisible or absent. 



