Reviews — Wachsmuth ^ Springer's Monograph on Crinoids. 117 



the two formations are not faulted together, nor in the rocks them- 

 selves is there any indication of the immediate neighbourhood of 

 a shore-line, or of a land-barrier having separated the Flintshire 

 from the Denbighshire areas. Had such a feature as the Vale existed 

 when the Carboniferous epoch commenced, the Basement Con- 

 glomerates of that foi'mation would have certainly revealed it. As 

 a fact, they are almost wholly absent along the Flintshire escarpment 

 and along the east side of the Vale of Clwyd, and though they appear 

 in an attenuated form at the north-east end of the Vale and extend 

 continuously from the south-west end near Llanelidan past Denbigh 

 and Abergele to Colwyn Bay,^ they always tend to develop in 

 thickness and in coarseness of conglomerate northwards and west- 

 wards, but neither in the Vale, nor along it, but away from it. 



The history of the Vale of Clwyd commenced, therefore, by the 

 formation of a deep faulted syncline during the great disturbances 

 which affected all the British area at the close of the Carboniferous 

 epoch. During the Continental period to which those disturbances 

 led, the Carboniferous rocks were deeply denuded from the anticlinal 

 regions, but preserved in the synclinal folds. Upon the faulted and 

 tilted remnant thus left in the Vale of Clwyd, the New Red Sand- 

 stone was overspread, probably overlapping it, though how far no 

 evidence has been left to show. Long subsequently, not improbably 

 in Miocene times, a new and widespread disturbance caused renewal 

 of movement alous: the old fractures, and threw the New Red Sand- 

 stone also into the form of a faulted trough, at the same time that it 

 must have emphasized the already existing syncline in the underlying 

 Carbonifei'ous strata. 



la IE "V I E "VsT s. 



I. — Wachsmuth and Springer's Monograph on Crinoids.^ 

 Sixth and Final Notice. 



WE have now considered the Introductory and Morphological 

 Parts of this great work. But these, though of more general 

 interest, serve but as foundation for the main structure, the 

 systematic account of the North American Camerate crinoids. This 

 Systematic Part occupies 695 of the large quarto pages, a bulk that 

 may astonish those who regard the Crinoidea as quite a small class. 

 Really the system of the crinoids is assuming considerable pro- 

 portions ; he who would master it must know the literary history of 

 nearly 450 names, and must be prepared to classify some 250 valid 

 genera. Moreover, the number of known genera and species in- 

 creases with alarming rapidity ; 13 genera and 250 species were 

 described as new during 1896 and 1897. 



1 Quart. Joui-n. Geol. Soc, vol. xxxv, p. 268 (1879). 



^ The North American Crinoidea Canierata. By C. Wachsmuth and F. Springer. 

 Mem. Mus. Comp. Zool. Harvard, vols, xx and xxi, containing 838 pp. and 83 plates. 

 (Cambridge, U.S.A., May, 1897.) For First, Second, Third, Fourth, and Fifth 

 Notices, see Geol. Mag. for June, July, September, and November, 1898, and 

 January, 1899. 



