J. Parkinson — Geology of the Gold Coast Littoral. 265 



is described in several characteristic genera. A distinction is drawn 

 between phyllodal and hypophyllodal structures. A trisei'ial arrange- 

 ment of the ambulacral pores is shown to correspond with some 

 degree of phyllode development. The importance of the structure 

 from the point of view of classification is discussed. Emphasis is 

 laid upon the close relationship between the Holectypoida and 

 Echinoneidae. The Cassidulidse are regarded as a composite group, 

 divisible into two sections (roughly the Jurassic-Cretaceous and the 

 Cretaceous-Kecent groups), the former being direct descendants of 

 Galeropygus, while the latter, from the same source, slowly attain 

 the Cassidulid character through the medium of the Jurassic 

 JNiicleolitidce. 



LlTERATUEE REFERRED TO. 

 1872. A. Agassiz, " Eevision of the Echini": Mem. Mus. Comp. Zool. 



Harvard, vol. iii. 

 1909. Id., " On the existence of Teeth and of a Lantern in the genus 



EcliinonMus, Van Phels " : Amer. Journ. Sci., ser. rv, vol. xxviii. 



1909. F. A. Bather, "Triassic Echinoderms of Bakony" : Besult. wissensch. 



Erforsch. des Balatonsees, Band i, Teil i, Pal. Anhang, Budapest. 

 1869. G. Cotteau, PaUontologie Francaise '■ : Terrain jurassiqiie. Tome ix : 



Echinides irreguliers. 

 1900. J. W. Gregory. "The Echinoidea " in Lankester's Treatise of 



Zoology, vol. iii. 



1910. H. L. Hawkins, " Some Ambulacral Structures in the Holectypoida " : 



Geol. Mag., n.s., Vol. VII. • 



1911. Id., " On the Teeth and Buccal Structures in the genus Conuhis, 



Leske": ibid., Vol. VIII. 



EXPLANATION OF PLATE XIII. 

 The figures are all slightly diagrammatic, and enlarged to the same size 

 regardless of their relative proportions. 

 FlG. 1. Arrangement of pores in phyllode of Ecliinolampas depresses. 

 ,, 2. Diagram of the principle of Holectypoid plate-crushing. 

 ,, 3. Hypophyllode of Pygaster scmisulcatus. 

 ,, 4. Hypophyllode of Galeropygus agariciformis. 

 ,, 5. Hypophyllode of Trematopygus faring clonensis. 

 ,, 6. Phyllode of Clypeus luigi. 

 ,, 7. Phyllode of G. ploti. 

 ,, 8. Phyllode of Py gurus michelini. 

 ,, 9. Phyllode of Catopygus carinatus. 



IV. — A Note on the Geology of the Littoral of the Gold Coast 



Colony between Elmina and Sekondi, West Coast of Africa. 



By John Parkinson, M.A., F.G.S., etc. 



THE following note on the rocks of the shore-line of part of the 

 Gold Coast Colony are a result of a short journey I undertook 

 there in 1910. On that occasion I landed at Cape Coast Castle and 

 travelled westward, staying successively at Elmina, Chama, and Sekondi. 

 Starting along the coast at Elmina, the coarse granitoid gneiss of 

 Cape Coast Castle, a rock rather poor in ferromagnesian minerals, 

 is left behind at a point some two miles to the east, and is replaced 

 by red grits or arkoses, which have a slight dip to the westward. 

 These beds have frequent ironstone partings, two or three inches 

 in thickness, and are often cross- veined with a similar material ; 

 doubtless, therefore, this is a secondary structure due to the deposition, 



