1872.] ETHEEIDGE— K^EAV ECniXODERlI. 101 



In the slight development of the posterior and lateral fimbriations 

 and in the position of the mouth and vent, Rotuloidea has affinity with 

 the Martinican genus Moidinsia, Ag. ; but the entire margin, as well 

 as the dorsal and ventral surfaces, of Moulinsia is crenulated ; the 

 elements of the apical disk, also, at once remove it from that genus. 

 The same comparison may apply to the genus Buna, Ag., from the 

 Tertiary beds of Bordeaux and Palermo, in whose crenulated or fimbri- 

 ated margin, as well as the position of the mouth and vent, there is 

 much resemblauce to the new form ; but the affinity disappears upon 

 comparing the ambulacra of the dorsal surface with those of Rotu- 

 loidea : both nevertheless belong to one group of Urchins. But 

 for the depression of the test, the position of the anal aperture, the 

 grooved avenues on the base carrying the ambulacra, and the lobed 

 peristome, this genus might almost be referred to Ft/gums (amongst 

 the Echinolamindo}) of the Oolites and Cretaceous rocks of Europe ; 

 for the margin of many forms of that genus is broadly and strongly 

 lobed (notably so in P. Blumenbachii). Again, the apical disk and 

 dorsal aspect have strong resemblance to those of Pyguriis, and also 

 of Chjpeus Plott'd ; and the wandering ambulacra at the base of 

 Rotidoidea give it an affinity to the digitate Pyguri of the Oolitic 

 rocks. 



The Urchins of this singular group in their recent state seem to 

 be confined to the western coast of Africa, near Senegal ; and I be- 

 lieve the specimens brought by Mr. Maw are the first of the true 

 Botuline type ever found fossil. 



Geological position. — In assigning to Rotuloidea its horizon in time, 

 I believe it to be Miocene, and an extinct genus ; it is associated with 

 Miocene species, and would seem to be the earliest known form of the 

 Kotuline group. 



Discrssiox. 



Mr. Ball, as an Alpine traveller who had also visited the Atlas 

 in company with Dr. Hooker and Mr. Maw, offered a few remarks. 

 The plain of Morocco was not, in his opinion, a level, but an inclined 

 plane, rising gradually in height up to the foot of the mountain, so 

 that the base of the boulder ridges was at some height above the 

 level of the plain near Morocco. He did not think that the boulder 

 deposits could be safely attributed to glaciers, but thought rather 

 that they had been carried into and deposited in a shallow sea. ^ He 

 thought also that Mr. Maw had somewhat overestimated the thick- 

 ness of some of the boulder deposits ; and though there was one in- 

 stance of an undoubted moraine in one of the higher valleys of the 

 Atlas, yet he could not agree in the view that the glaciation of the 

 Atlas was general. He could not accej)t such a great thickness of 

 beds as that represented by the vertical shales in Mr. Maw's section. 



Prof. Ramsay was pleased that the author, though giving so many 

 interesting details, had not assigned any definite age to many of the 

 beds. He agreed with him as to the cause assigned for the great 

 tufaceous coating of the country. He had already assigned the 

 same cause for the existence of certain saline beds, and would attri- 

 bute the existence of the great coating of gypsum at a slight depth 



YOJ,. XXVITT. rAET T. J 



