1872.] EIHEEIDGE — NEW ECHINODEBM. 97 



(15) A slight subsidence of the coast-line, now going on, with 

 an accumulation of extensive deposits of blown sand at Mogador. 



(16) The formation of a tufaceous surface-crust over almost the 

 entire plain of Morocco, due to the drawing up to the surface, by- 

 rapid evaporation, of water from the subjacent calcareous strata, 

 depositing, laj^er by layer, laminated carbonate of lime. 



EXPLANATION OF PLATE III. 



Fig. 1. Sketch section across the plain of Morocco to the watershed of the 

 Great Atlas. 



2. Cliff-section at Saffe. 



3. Section of the Tufa-crust covering the plain of Morocco. 



4. Surface of ditto. 



5. Section of boulder-mounds skirting the escarpment of the Atlas plateau. 



6. Front view of the escarpment and boulder-mounds. 



Appendix to Mk. Maw's Paper on the Geology 0/ Morocco, being 

 a Description of a New Genus of Possil Scutelloid Echinoderm 

 from Saffe, N. Africa. By E. Etheridge, Esq., E.R.S., F.G.S. 



Amongst the specimens brought by Dr. Hooker and Mr. G. Maw, 

 from Morocco, in North Africa, and submitted to me for examination, 

 were some Urchins of the family ScutelUdce, of peculiar form, diifering 

 from any I had previously seen or examined, and certainly not re- 

 ferable to any described Tertiary species. Comparison with known 

 forms, recent and fossil, failed to elucidate their true history more 

 than to show that they evidently belonged to the Rotuline group of 

 Scutellidce amongst the Clypeasteroidea, nevertheless diflfering con- 

 siderably from the genus Botula (Klein) the only form to which 

 they can be referred. 



Rotula now inhabits the sea and coast of Senegal, "West Africa, from 

 which two, if not three, species are known : — B. RumpJiii, Klein ; R. 

 Augusti, Elein ; and R. Gaulteri, Ag. There is, however, a marked dif- 

 ference between the characters of our new genus and that of Rotula, 

 especially in the more elongated and oval form of the test, the extreme 

 rounding or truncation of the fimbriation, or crenulation, upon the 

 posterior margin, more acute anterior and less tumid lateral margins, — 

 so much so, that a line drawn round the circumference of the test of 

 Rotula., including the digitations, would describe a complete circle 

 touching the periphery of the Urchin, whereas the form of Rotuloidea 

 is an oval or ellipse — Rotula being circular, Rotuloidea oval ; these, 

 with other differences to be hereafter noticed, justify the establish- 

 ment of a new genus for the reception of these North-African, 

 fossil forms. The resemblance to and affinities with Rotula suggest 

 the name Rotuloidea. 



It is of no small interest thus to obtain from the Great Morocco 

 plain south of Saffe, at "Jew's cliff" &o., what appears to be a less- 

 developed or lower type of Clypeasteroid, which must have been an 

 abundant species in the Miocene sea of that area, then extending far 



