D1THYR0CARIS TESTUDINEA. 151 



ventral faces on the shale, and these appear to have been sulcate, with granula- 

 tions (possibly adventitious) on the median ridge. The dorsal faces have only a 

 small portion of the top end of each preserved, showing a median ridge, and 

 otherwise sulcate. 



This may belong to a small variety or a young form of the normal D. testudinea. 



It is comparable in size with the trifid of Ceratiocaris minuta of our ' Mono- 

 graph Brit. Paheoz. Phyll.,' 1888, p. 47, pi. x, fig. 11, and pi. xi, fig. 10. 



In black shale, non-calcareous. Bast Kilbride. Paton Coll. 



PI. XXIII, fig. 8. Brit. Mus. 59541, No. 29. 



Size. — Penultimate segment 3 mm. long in its most perfect part. Ultimate 

 segment 6 mm. long ; style obscure ; stylets 13 mm. long. 



Characters. — The penultimate segment is marked with transverse wavy lines 

 and the ultimate with oblique lines ; thus comparable with D. testudinea. 



In this small tail-piece the three spines have been pressed together, and one of 

 them (the style) is quite obscured as to character and relative size. The two 

 largest spines are cercopods (stylets) of equal length, and are sulcate. 



This little specimen, in dark-grey calcareous shale, was collected by the late 

 Dr. Rankin in Lanarkshire. 



PL XXVII, figs. 3 a, b. Neilson Coll., H. 

 Size. — Length about 34 mm.; width about 2 mm. 



Characters. — A small, delicate specimen of an isolated dorsal crest like that 

 attached to the valve shown in PI. XXVIII, fig. 1. 



In black shale, slightly calcareous. Kirktonholm, East Kilbride. 



PI. XXVIII, figs. 1 a. b. Neilson Coll., D. 



Size, — Length, including the spine, about 85 mm. ; width about 37 mm. 



Characters. — The right-hand moiety (magnified) of a good carapace of D. 

 testudinea, having besides its usual characteristics a well-marked cristate dorsal 

 ridge, which is absent in all the specimens hitherto described. A separate 

 example, however, of such a dorsal ridge is also preserved in Mr. Neilson's cabinet 

 (PI. XXVII, fig. 3). 



Black shale, non-calcareous. East Kilbride. 



PI. XXVIII, fig. 2. Neilson Coll., C. 



Size. — Width at the top of the piece about 35 mm. ; width between the points 

 of the two spines 24 mm. ; width between the bases of the two spines 20 mm. 



Characters. — The posterior portion of a well-preserved right-hand moiety or 

 valve of D. testudinea, showing the exact form of the hinder edge and the two 

 posterior spines. 



Black calcareous shale. East Kilbride. 



