250 BRITISH FOSSIL CRUSTACEA. 



elytra-like lobes, to the posterior border. The anterior and expanded end of this dorsal 

 ridge is ornamented on either side, at its union with the cervical furrow, by two small 

 crescent-shaped lobes. 



The surface of the carapace is everywhere smooth and devoid alike of tubercles and 

 puncta. 



Species 2.— CYCLUS TOROSUS :— H. Woodw., 1870. Woodcut, fig. 80, a, b. 



Cyclus torosus, H. Woodw., 1870. Geol. Mag., vol. vii, p. 5.55, pi. xxiii, figs, 4 



and 4 a. 

 — — . H. Woodw., 1873. Brit. Assoc. Reports, 7th Report on Fossil 



Crustacea, p. 304. 



Fig. 80. — Cyclus torosus, H. Woodw. 

 a, dorsal aspect; b, profile; * indicates the anterior border of shield. 



The buckler in this species is nearly circular, and is 4 lines in diameter. Its dorsal 

 line (viewed in profile) is very tumid, and is elevated 2 lines above its border (see fig. 80, b). 

 The cervical furrow divides the carapace transversely into two nearly equal parts (in 

 this respect offering a marked contrast to C. bilobatus); the anterior moiety is divided into 

 eight lobes, and the posterior into three. A narrow, slightly flattened border appears to 

 have nearly, if not quite, surrounded the shield. 1 



In front of the carapace is a median, somewhat triangular lobe, having its rounded 

 apex directed backwards ; this is flanked on either side by two nearly round lobes, two 

 placed subcentrally and two near each latero-anterior border. Uniting these five anterior 

 lobes with the cervical furrow are two lateral five-angled lobes and a central seven 

 angled (cardiac P) lobe or area. Behind the cervical furrow a dorsal ridge, of marked 

 elevation, divides k the posterior half of the carapace into two rounded lobes, which nearly 

 unite behind — being only separated by a narrow dorsal ridge — but are widely separated 

 in front, not only by the interposition of the dorsal ridge — which expands like the head 

 of a pillar before reaching the cervical furrow — but also by the intercalation of two 

 narrow lobes or ridges on either side of the expanded dorsal ridge. The even contour of 

 1 Several of these forms may have been destitute of a rim in front (see Halici/ne, PI. XXXII, figs. 48 and 49). 



