ACIDASPIS LALAGE. 117 



Remarks. — There is not much to add to this description. The characters of 

 the head-shield sufficiently distinguish it from A. lalage. The anterior and 

 posterior ridges of the pleurae of the thorax bear a single row of relatively 

 large coarse tubercles ; and in the pygidium the second axial segment is longer 

 than the first ring, and of a subquadrate shape. The axis is about one fourth to 

 one fifth the width of the pygidium. There is no distinct border, and the surface 

 is coarsely tuberculated up to the bases of the spines, which are fourteen in 

 number. In the thorax the axis is about one fifth the width of the whole body, 

 being therefore narrower than in A. grayse and A. lalage. 



The specimen attributed to A. lalage by Nicholson and Etheridge {up. eit., 

 pi. viii, fig. 17) consists of a thorax with the axis and pleurae possessing the 

 essential characters of A. hystrix ; the position and size of the pleural groove and 

 of the bounding ridges, the character of their ornamentation, and the size and 

 relation of the distal spines agree precisely. It is unfortunate that the head-shield 

 is not better preserved. The figures given by Nicholson and Etheridge leave 

 something to be desired. 



Collections. — Mrs. Gray (f. M.) ; Museum of Practical Geology ; Edinburgh 

 Museum. 



Horizon and Localities. — Balclatchie Group (Llandeilo) : Balclatchie; Pen- 

 whapple Glen. 



7. Acidaspis lalage, Wyville Thomson, 1857. Plate XVI, fig. C. 



1857. Acidaspis lalage, Wyville Thomson, Quart. Journ. Geol. Soc, vol. xiii, p. 206, pi. vi, figs. 1—5. 



1876. Acidaspis lalage, Armstrong and Young, Cat. West. Scot. Foss., p. 15. 



1877. Acidaspis lalage, Woodward, Cat. Brit. Foss. Crust., p. 19. 



1878. Acidaspis lalage, Nicholson and Etheridge (e. ^.),Mon. Silur. Foss. G-irvan, fasc. i, p. 121, 

 pi. viii, figs. 20, 21, 22 (wow figs. 17, 18, 19). 



1899. Acidaspis lalage, Mem. Geol. Surv., Silur. Rocks Brit., vol. i, Scotland, pp. 510, 688. 



Specific Characters. — "Not above half an inch long. General form broad, 

 rather square. Head broad and short. Glabella triangular ; median lobe broad, 

 not very prominent. Two oval side lobes entirely circumscribed, separated from 

 the median lobe by distinct furrows. Portion of the cheek within the facial suture 

 very gibbous. Ocular ridge distinct. Eyes somewhat remote. Neck-segment 

 separated from the median lobe of the glabella by a shallow groove; gibbous, and 

 continued backward into two long, diverging, straight, or curved spines. Axis of 

 thorax and abdomen narrow, prominent. Body-rings nine; lateral portions hori- 

 zontal, convex; a longitudinal furrow separates the convexity into two ridges, 

 which coalesce at the distal extremity, and end in a long, slightly recurved spine. 



