DITHYROCARIS LATERALIS. 185 



PI. XXIII, fig. 6. Mas. Univ. Cambridge. 



DiTHrROCARis LATEEALis, M'Coy, 1851. Brit. Pal. Foss. Cambridge Mus., 



fasc. 1, p. 182, pi. 3 I, fig. 36. 



— — Morris, 1854. Catal. Brit. Foss., edit. 2, p. 107. 



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



p. 64. 



— — Etheridge, 1888. Brit. Foss., vol. i, Palaeoz., p. 238. 



Size and Characters. — A trifid caudal appendage, showing the dorsal aspect ; 

 both the telson (style) and the cercopods (stylets) are imperfect at their proximal 

 ends ; but they measure, approximately — the style, 25 mm. ; the stylets, 36 mm. 

 in length. The former is bayonet-shaped, with a mid-rib ; the latter, coarsely 

 striate or sulcate, with four costulse, are longer than the style. This trifid may 

 possibly belong to Dithyrocaris testudinea or a closely allied form. The figure 

 referred to above as given in the ' Brit. Pal. Foss. Cambridge ' is partly a restora- 

 tion, not quite matching the specimen in the University Museum. 



" From the black beds over the Main Limestone of Derbyshire." W. Hopkins 

 Coll. 



The following remarks on this specimen (fig. 6) are given in M'Coy's ' Pal. 

 Foss. Cambridge Mus.,' fasc. i, 1851, p. 182 : 



" I have examined four species [of Dithyrocaris] from the Carboniferous rocks of Ireland, but 

 the only British example I have seen is a specimen in the collection [Cambridge] from the black 

 Carboniferous Limestone of Derbyshire, indistinctly preserved, but most probably the tripartite tail 

 of a new species, allied to D. Colei (Portl.), ' Geol. Rep.,' pi. xii, and to the D. Scouleri (M'Coy) 

 figured in my ' Synopsis of the Carb. Foss. of Ireland,' pi. xxiii, fig. 2, from the black shales of 

 Aughnaclough, Clogher. 



" In this species the central angularly ridged spine is about ten lines long ; the tvFO lateral 

 spines about one inch five lines long, coarsely sulcated longitudinally with only three or four strong 

 ridges ; this great excess of the lateral over the medial spine seems to characterise the species very 

 well, and I would provisionally call it Dithyrocaris lateralis (M'Coy) ; when imperfect, the coarseness 

 of the few large sulci of the lateral spines easily distinguishes those parts from the two figured species 

 alluded to." 



PI. XXIII, fig. 5. Mus. Geol. Surv. Scotl., m 4267 \ No. 25, F rui and 

 m 4268* (counterparts). 



Size and Characters. — This trifid tail-piece closely corresponds with M'Coy's 

 D. lateralis ; but shows the ventral aspect. The style is bayonet-shaped, measuring 

 31 mm. in length; the stylets are 42 mm. long, striate; all have adventitious 

 granulations. Their proximal ends are more perfect than in the Cambridge speci- 

 men of D. lateralis. 



From Tweeden Burn, 250 j^ards above its mouth, near New Castleton, Rox- 

 burghshire. 



25 



