Yol. 57.] PHYSICAL DEVELOPMENT OF ST. KITTS, ETC. 537 



have been accompanied by an eruption. Owing to these two 

 volcanic uplifts, the limestones which underlie the submerged 

 coastal plains may be seen, for they appear nowhere else on these 

 islands. These deposits are composed of white marls, of soft earthy 

 texture, but compact in places. The surfaces are case-hardened 

 from exposure to the weather. Fossils are abundant at certain 

 points, but the shells are mostly in the form of casts, although some 

 are better preserved in the volcanic sands (these are also cal- 

 careous) which immediately underlie the marls. The echinoids are 

 in a better state of preservation, as are also the corals, which 

 Dr. T. Wayland Yaughan kindly determined for me : — Orbicella 

 cavernosa, Linn., 0. acropora, Linn., Siderastrcea siderea,^\l. & Sol., 

 all of which are living species. Orbicella acrojoora is the most 

 common form on the island of Sombrero. The shells were also 

 kindly determined for me by Mr. Charles T. Simpson : — Venvs can- 

 cellata, Linn., V. Paphia, Linn., Cardium suhlongatum, Sow., Glyci- 

 meris pectinatus, Gl. undatus, Lam., Lutricola interstriata^ Say, 

 TelUna interrupta, Wood, and Pecten ziczac, Linn. ? These are all 

 living species. Mr. Cleve seems to have found a still larger 

 number of species, and among them a Modiola, not living in the 

 Caribbean Sea, though closely related to a species existing in 

 northern waters. He also obtained Tellina Gruneri, Phil., a shell 

 rarely found in the adjacent seas, but occurring in the Miocene 

 strata of Cuba and Puerto Rico ; consequently he was disposed to 

 regard the formation as newer Pliocene or Pleistocene. From the 

 evidence, the deposit cannot be older, but the fossils do not tell us 

 to which epoch, since the later days of the Pliocene Period, they 

 belong ; it is necessary therefore to base this determination upon 

 physical resemblances and the general succession of events in the 

 whole region. The formation appears to correspond to the surface- 

 marls of Sombrero, the upper marls of Anguilla, and those at the 

 Usine of Pointe a Pitre in Guadeloupe. These have about the same 

 thickness, contain a similar fauna, and are regarded as the 

 equivalent of the Lafayette formation of the American continent, 

 belonging to the time about the close of the Pliocene Period. 

 Their drowned surfaces present erosion-features of considerable age, 

 which will be considered again (p. 540). The elevation of the 

 volcanic domes of Brimstone Hill and The Quill are of a very much 

 later date. 



Y. The St. Kitts Gravels. 



While the surface of the island is covered with washes of volcanic 

 debris, there are some sections along the coast having a height of 

 50 feet. Between Basse Terre and Old Road, for a distance of 

 about a mile, the strata are seen to be composed of rounded gravels, 

 some pebbles having a diameter of 4 to 8 inches, intermingled 

 with more or less angular material, which had been carried into 

 the sea by the rain-washes during the accumulation of the gravels. 

 This gravel-formation is seen to be dissected, as shown in the 

 accompanying figure (p. 538), by a ravine about 100 feet wide, which 



Q. J. G. S. No. 228. 2 o 



