150 BRITISH PALAEOZOIC PHYLLOCARIDA. 



A small Posidonomya lies in the shale near the end of one of the stylets, and 

 another at the ventral edge of the right valve near by. 



In black shale, slightly calcareous. From East Kilbride. 



PI. XXI, fig. 5; PI. XXXI, fig. 4 (magnified). Brit. Mus. 59541, No. 27. 



Size. — All the three caudal spines are imperfect at the distal ends. The 

 longest stylet is about 30 mm. ; the style 20 mm. without the head and the tip. 



Characters. — This specimen shows an impression of the dorsal surface of part 

 of the ultimate segment, and the under (ventral) surfaces of three tail-spines. 

 The impress of the segment is smooth in appearance, but bears the characteristic 

 chevron-lines and obliquely striated interspaces. The caudal plate at the head of 

 the trifid is lost. 



The spines are apparently smooth, but really delicately striated or ridged. 



The style shows by the impress of upper (forward) part that it was striate; 

 and its lower moiety bears a single smooth ridge on its ventral aspect, with a 

 broad smooth furrow on each side of it. 3y their impressions the stylets were 

 evidently costulate on the dorsal face, with fine, oblique, subsidiary striae on the 

 sides of the four or five riblets ; and on the ventral face each has three costulae, 

 marked with delicate, close-set chevrons, pointing downwards (backwards), their 

 side-lines making oblique subsidiary strias. They show pits for bases of hairs. 



In black non-calcareous shale; East Kilbride. There is a Posidonomya on the 

 shale, small, with concentric irregular undulations. 



PI. XXI, fig. 6; PI. XXXI, fig. 3 (ornament). Mus. Sci. and Art Edinb., 

 Coutts, 1887, ||, No. 12. 



Size. — Length of valve, imperfect, 30 mm. ; breadth of valve about 16 mm. 



Characters. — A right valve (or moiety of carapace) imperfect in front and at 

 the dorsal edge ; more convex than fig. 3, and with thicker test ; it has similar 

 characteristic lineation and minutely punctate interspaces (PI. XXXI, fig. 3). 

 Ventral fringe strong in the posterior part, and narrowing forwards as far 

 as seen. 



In black calcareous shale. From East Kilbride. 



PL XXIII, fig. 7. Brit, Mus. 59541, No. 30. 



Size. — Carapace 27 mm. long, 18 mm. wide; style 10 mm. long; stylets (pro- 

 bably shortened by fracture) 9 mm. long. 



Characters. — This small trifid tail-piece is attached to a subconvex, oval cast 

 (not figured) of a little Dithyrocaris testudinea, badly preserved, but retaining its 

 length and width, and some of the characteristic lineation, directed obliquely 

 backwards, outside the mesolateral ridges. The details of character are rather 

 obscure. The distal parts of the trifid have left impressions of the lower or 



