490 Dr. Henry Wood/card — JVote on Ct/chis Johnsoni. 



about half. On the east coast of Scotland it is scarcely 30 inches. 

 When we consider how the ice grows upon heavil}' snowed regions, 

 owing to the continual storage from year to year, we may easily 

 imagine what an enormous excess must have resulted on the west 

 side of Scotland. In fact, we know this from the state of matters 

 that existed in Inverness-shire just before the glacier lake of Glen 

 Roy was formed, when the western ice overflowed all the passes on 

 the east side of the Great Glen, although these passes are actually 

 higher than those on the west, which led out to the Atlantic. This 

 difference between the two sides of the country in regard to the 

 amount of ice that lay upon them has never been adequately 

 realized, although it affords the only true means of explaining man}' 

 remarkable features in the character of the surface, and I think it 

 might be sufficient to account for that depression of the western side 

 which led to the formation of the Clyde beds. 



III. — Further Note on Cyclus Johxsom, from the Coal- 

 measures NEAR Dudley. 



By Hexry Woodward, LL.D., F.R.S., Y.P.Z.S., F.G.S. 



MY friend Professor Lapworth kindly sent me, for identification, 

 in July last the split portions of two nodules containing 

 examples of the interesting little Crustacean genus Cyclus, from the 

 ' Peniiystone ' Ironstone of the Coal-measures near Dudley, obtained 

 by Miss Ethel M. R. Wood, M.Sc, of the University of Birmingham, 

 and I have obtained permission to publish a note thereon, supple- 

 mentary to my paper in 1894.^ In that paper I described, among 

 other species, one which I named Cyclus Johnsoni (op. cit.. Pi. XV. 

 Figs. 4-7, pp. 537-538), from the Coal-measures, Coseley, near 

 Dudley, which is identical with Miss Wood's specimens. As one of 

 these latter displays some further details of appendages I have given 

 a figure of it here as tending better to elucidate the structure of this 

 curious genus. (See Woodcut on p. 491.) 



This specimen shows the broad, raised, and grooved margin of the 

 shield- or disc-like carapace, the centre of which is removed and 

 displays, as in Cyclus Eankini (op. cit., PI. XV, Fig. 8), the radiating 

 ridges of the ventral or sternal arches once giving attachment to 

 seven or more pairs of simple swimming- or walking-feet, each having 

 been no doubt furnished with an endopodite and exopodite, as in the 

 limbs of Trilobites,^ subserving the purposes of branchiae and limbs, 

 the bases being perhaps also maxilla?, or they may have been 

 furnished with such simple appendages as are seen in the larval 

 stages of modern Limidus.^ 



1 See " Contributious to our Knowledge of the genus Cyclus, from the Carboni- 

 ferous Formation of various British localities" : Geol. Mag., 1894, pp. 530-539, 

 Plate XV. 



■^ C. D. AYalcott : Geol. Mag., 1894, p. 246, PI. YIII, Fig. 6. C. E. Beecher : 

 Geol. Mag., 1896, p. 193, PI. IX. 



^ See Mon. Brit. Foss. Crustacea, Order Merostomata, by H. Woodward, pt. r, 

 pp. 214-218, pi. xxxiii and explanation: Pal. Soc. Mon., 1878. 



