142 BRITISH PAL.'EOZOIC PHYLLOCAUIDA. 



3. DiTHYHOCAius GHANCLATA, WudJ icard and EfJifiridr/e, 187S. Plate XVIII, figs. 4, 



a, h, 6 ; Plate XIX, figs. 5, 6 a, o ; 

 Plate XX, figs. 1 «., b, 2 a—d, 3 a— r/. 



DiTUVEOCAEis GHAKULATj, H. Wooduarcl and R. Etheridge, jun., 1873. Mem. 



Geol. Surv. Scotl., Explan. Sheet 23, 

 Appendix, p. 99. 



— — W. and E., lS7i. Geol. Mag., dec. 2, vol. i, p. 1(»8, 



])1. V, fig. 3 ; and Report Brit. Assoc for 

 1873 (1874), Sections, p. 92. 



— — J. Armstrong, 1S76. Catal. W.-Scot. Fossils, p. 45. 



— ~ H. Woodward, 1877. Catal. Brit. Foss. Crust., p. 73. 



— — Biffsly, 1878. Thesaur. Dev.-Carb., p. 249. 



— J. Coults, 1844-5. Trans. Geol. Soc. Glasgow, vol. 



vii, lip. 200 and 327. 



— — E., W., and J., 1887. Eep. Brit. Assoc, for 1886 



(1887), p. 64. 



— — Etheridge, 18SS. Foss. Brit., vol. i, Palffoz., p. 238. 



Specific Characters. — Dithyrocaris granulata is very similar to D. glalra ; but 

 it has on each valve a definite mesial (mesolateral) ridge ; and an abundant 

 granulation on the anterior and dorsal regions. These features distinguish 

 this species from JJ. glabra. Moreover the medio-dorsal ridge, with its side- 

 flanges, is perhaps more strong developed. It remains attached to a valve, and 

 perfect, in PI. XVIII, fig. 4, and PI. XX, fig. 2 a ; and a portion of it overrides the 

 two dorsal edges of an open carapace in PI. XVIII, fig. 6, and PI. XX, fig. 1 a. 



PI. XVIII, fig. 4, and PI. XX, fig. 2 a—d (magnified). Mus. Geol. Surv. 

 Scotl., F \^, No. 6. 



Size. — Length of valve, 40 mm., including the spines; breadth of valve, 

 18 mm. 



Characters. — A single left valve semi-elliptical, that is, having the shape of the 

 moiety of an ellipse that has been divided longitudinally into two halves. The 

 dorsal edge is straight ; the ventral has a symmetrical elliptical curve. The ends 

 differ ; the anterior, defined by the rising and narrowing curve of the ventral 

 border, beai'S a short antero-dorsal process, above which (to the right or left in 

 the figures) the dorsal border begins with an ogee curvature. The posterior end 

 is moi-e broadly curved, but turned in suddenly to meet the junction-line of the 

 valves, so that the dorsal border ends in a medial recess. The hinder border, 

 moreover, is marked by a strong, postero-ventral, triangular, flat, sharp spine. 



