D1THYR0CARIS TESTUDINEA. 149 



of its fringe ; but the impression of the longitudinal striae of its under surface is 

 present. 



In " Coal-shale," black and calcareous, Carluke. Morris Coll. 



PL XXI, fig. 3 ; PI. XXXI, fig. 2 (ornament). Mus. Sci. and Art Ediub., 

 Coutts, 1887, ||, No. 13. 



Size. — Length of valve, imperfect in front, 28 mm. ; breadth of valve 15 mm. 



Characters. — Right valve (or moiety of carapace) semi-elliptical ; with a very 

 thin film of the test, flattened, smooth, bearing numerous delicate, sinuous lines 

 passing obliquely from the dorsal region to the mesial ridge, and, coinciding with 

 the angular lines of its chevron-like ruga} ; passing on to the ventral border, they 

 are deflected forwards, as usual in D. testudinea. The spaces between the lines 

 are closely pitted with very minute puncta (PI. XXXI, fig. 2). There are the 

 usual small sigmoidal cephalic ridge and thin short nuchal ridge ; not clear in 

 the figure. 



The dorsal edge is simple ; very slightly bent at the nuchal ridge, and damaged 

 at its posterior end. The postero-ventral spine is proportionally strong ; the 

 ventral edge is fringed as far as it is clear of the matrix. 



Black slightly calcareous shale. Probably from East Kilbride. 



PI. XXI, fig. 4. Mus. Sci. and Art Edinb., Coutts, 18S7, ff> No. 11. 



Size. — Length of one valve (the right), including the spine, 38 mm.; breadth 

 of valve about 18 mm. ; of the abdominal segmsnts exposed, the ultimate and part 

 of penultimate, 10 mm.; style, 11 mm. ; stylets about 15 mm. 



Characters. — This specimen represents a right and a left valve and the 

 caudal extremity, all displaced and crashed. The abdomiual segments and tail 

 have not been removed far from the posterior extremity of the left valve ; and 

 the hinder part of the right valve lies at a right angle over the postero-dorsal 

 region of the left valve, near both of which, indeed, the caudal portion is situated. 

 Both valves show evidences of the ventral fringe, the ridges, and the paculiar 

 lineation of D. testudinea. 



The abdominal (ultimate) segment that is exposed has been turned over, so as 

 to show its lower or ventral aspect. It has rather sinuous chevron-lines crossing 

 it, with their bluntish angles looking backwards. Of the three tail-spines the 

 style (in the middle) is the shortest ; it shows a flat, smooth surface (ventral), and 

 probably was of a bayonet-shape. The others are much longer, convex, and 

 striated, coarsely at top, but more delicately towards the ends. The relative 

 position of the three spines shows that all the tail exposes the ventral aspect. 

 The mesolateral ridge of the left valve appears, by some accident, to be much 

 stronger (or better preserved) than that of the right valve. 



20 



