246 ME. A. J. JUKES-BROWNE ON H0LA8TEE ALTUS. [Aug. 1 898, 



but on the watershed between the valleys of the Umborne and 

 Offwell brooks, where the surface has been modelled chiefly by the 

 action of rain, the Greens and has resisted detrition better than 

 either the Chalk or the Red Marl, so that the ground falls away on 

 each side of the faulted strip, except where the Red Marl is capped 

 by Greensand, as on Widworthy Hill. This relation is shown in 

 the accompanying section (p. 245), which is drawn nearly east and 

 west through Widworthy Park. 



[It has been explained in the paper already referred to, ' On the 

 Delimitation of the Cenomanian,^ Hill & Jukes-Browne, Quart. 

 Journ. Geol. Soc. vol. lii (1896), and also in the note on p. 239, 

 that the calcareous sandstones of Wilmington and the Devon coast 

 are the local equivalents of the Chalk Marl, and that they form a 

 zone of Ammonites Mantelli, Between this zone and the suc- 

 ceeding one of RTiynchonella Cuvieri there is a break, with an 

 absence of anything to represent the upper part of the Lower 

 Chalk. 



Hence the succession of zones seen at Wilmington above the 

 Upper Greensand may be expressed as follows : — 



Feet. 



^ r Zone of Terehratulina gracilis ? 40 



IDRONIAN. I ^^ Bhynchonella Cuvieri 30 



n * / (Upper beds wanting.) 



UENOMANiAN. |2oueof^?ymomYesilfa«ifeZ^i 40 



—A. J. J.-B., April 22nd, 1898.] 



KOTE on HOLASTEK ALTUS, Ag. 



[Plate XXIV.] 



Among the commonest and most conspicuous fossils in the 

 Wilmington Sands are certain species of the genus Holaster. One 

 of them is Holaster Icevis, var. carinatus. Lam. ; but as the examples 

 of this form do not differ materially from those found elsewhere, 

 they need not detain us. 



In respect of those which are entered in the list on p. 245 

 as Holaster subglohosus, Leske, and Holaster alius, Ag., the case 

 is different ; for the species or variety altus has not previously been 

 discussed by any English echinologist, nor recorded from any English 

 locality, though it is well known in Prance. 



Holaster altus was first described and figured from a Swiss 

 specimen by Agassiz in 1839.^ He distinguished it from others 

 (1) by the great height of the test, (2) by the great width of the 

 ambulacral plates ; and he adds, ' There exist two well-marked 

 sulci (si lions) — one on the anterior face in which lies the odd 

 ambulacral area, the other on the posterior face.' Eurther, he 

 remarks : — * I do not hesitate to identify with this species several 



^ ' Descr. fichin. foss. de la Suisse,' p. 20 & pi. iii, figs. 9 & 10. 



