DITHYROCARIS INSIGNIS. 159 



reticular surface, having lines parallel with the lower edge, and feeble transverse 

 strias. A straight mesolateral rugose ridge is present, ending at the notch above 

 the postero-ventral spine ; the filmy surface of the valve bears a faint reticulation 

 (fig. 6 d), and there are some irregular accidental superficial inequalities. 



The funiculate pattern of the ventral margin is peculiar, though essentially of 

 the same nature as the more usual fringe. This form is apparently distinct from 

 the other specimens, and we may name it D, fimiculata. The narrow rigid shape 

 of the valve also distinguishes it from D. Colei (compare fig. 7 on the same plate). 

 On the same piece of thin black calcareous shale there is a filmy and imperfect 

 carapace of the same species. From the Calciferous Sandstone Group ; Tweeden 

 Burn, 250 yards above its mouth, New Castleton, Roxburghshire. There is a 

 fragment of the same species, from Tyrone, in the Brit. Mus., I 280. 



7. Dithyeooaris insignis, sp. nov. Plate XXV, figs. 3 a — c, 4, 5 a, b ; Plate XXVII, 



figs. 1 a, b, c ; Plate XXX, figs. 1—3 ; Plate XXXI, 

 figs. 6, 7 ; and var. multijugata, figs. 8 a, b, c, 9. 



Specific Characters. — Carapace relatively large, suborbicular or suboval; with 

 broad ventral margin ending in a long sharp spine on each side ; strong meso- 

 lateral, and weaker dorsal ridge. Posterior border straight between the two 

 postero-ventral spines, but projecting in the middle with the dorsal spine. The 

 surface has linear and reticulate ornament. 



PI. XXV, figs, 3, 4, and 5. Leeds Mus. Coll., Xos. 33 a and 44 a. 



Size. — From the mesolateral ridge to the ventral border 16 mm. 



Characters. — Crushed and much displaced fragments of one or more large 

 suborbicular carapaces on one slab. The mesolateral ridge and. the fringed ventral 

 border are well marked, and are like those in D. tricornis, &c. There is a faint 

 and rather curved elevation lying obliquely in the middle of the valve, probably 

 due to the test accidentally overlying some narrow fragment. The postero-ventral 

 border and its spine have been much damaged. The dorsal ridge has been broken 

 away in this specimen. 



The reticulation on one part of the surface (fig. 3 b) consists of delicate 

 raised, oblique, and sinuous stria?, interrupted and inosculating to form an 

 irregular network ; but on the right-hand side of the mesolateral ridge the main 

 strias are parallel with that ridge, and the network is therefore straighter. 

 Figs. 4 a — e show the features of the mesolateral ridge, the rugas passing down 

 into the general reticulation of the surface. When highly magnified, the meshes 



