CLLENOCARIS YOUNGII. L8] 



which essentially constitute angular rugae pointing backwards, as in Dithyrocaris. 

 At places on the surface one set of striae cross another set, making a definite 

 reticulation (fig. lie) near the mesolateral ridge; see also fig. 8 a, PI. XVIII; 

 elsewhere, in the front part of the valve, one set retain and the other lose their 

 continuity (fig. 11/). In this latter case the striae form continuous parallel lines, 

 with interspaces partially and irregularly traversed by short oblique lines (fig. 

 11/). Compare PI. XVIII, figs. 8 b and 8c; also compare F. A. Romer's 

 D. {?) Jaschei, 1855 (PI. XXIX, fig. 15 c). 



The specimen under notice exhibits the inturned edge of the ventral margin 

 very clearly, as shown in figs. 11 b and lie; it has a strong rim along the angle 

 of its bend, and another (slighter) along its lower or inner edge. 



From the Carboniferous Limestone of Settle, Yorkshire. J. H. Burrow Coll. 



PL XXXI, fig. 5. Mus. Univ. Cambridge. 



A small and imperfect left valve, here enlarged 3^ diameters, to show its 

 ornament of delicate, regular, parallel, longitudinal striae, reaching up to the 

 anterior region, and curving inwards to the middle ridge, and parallel to the 

 edge of the valve in the postero-ventral region. 



From Settle (Burrow Coll.). 



2. Ch.enocaris Youngii, sp. uov. Plate XXII, figs. 1 a — e. Dr. John Young's 



Coll. (Robroyston). 



Size. — Length 6 mm. ; width 3 mm. ; thickness of carapace, with the valves 

 partially closed (figs. 1 c and d), 2 - 4 mm. 



In its general aspect this little specimen closely resembles Oh. ten a 1st r lata, PL 

 XXI, figs. 8, 9, and 11. The relative position of the two moieties of the carapace 

 (PL XXII, fig. 1 (1) may indicate the natural stable condition in the life of the 

 animal, or may be due to the imperfect closing of the valves of this species, filled 

 in with the matrix of black shale. In its small size this specimen differs 

 from those described in the preceding pages : its cephalic ridge is not so 

 sigmoidal, and, owing to a curved sulcus behind it, seems to be raised on 

 a cushion-like elevation ; its surface is not at all striate, but punctulate, 

 especially near the mesolateral ridge, which is a prominent feature in this, as in 

 the other specimens. This ridge has minute lateral notches, formed by the inter- 

 spaces of the pitting being exaggerated into little buttresses of the ridge (fig. 1 e) ; 

 and these are very analogous to the junctions of the oblique striae with the ridge 

 in PL XXI, fig. 11 e, and not quite so closely to those in PL XXII, fig. 4. 



Owing to the distinctive features described above, we regard this as a new 



