Geological Society of London. 89 



4. Siliceous earths (Radiolarian). 



5. Calcareo-siliceous and chalky earths (Foraminiferal) . 



The whole series is more calcareous in the northern than in the 

 southern part of the island, and layers of volcanic dust occur in it 

 at various horizons. There is everywhere a passage from the more 

 siliceous to the more calcareous earths. 



From the palEeoutological and lithological evidence the authors 

 conclude that the depth of water in which the Oceanic beds were 

 deposited varied between 1000 and 2500 fathoms. The micro- 

 scopical and chemical evidence shows that the Radiolarian earths are 

 similar to modern Radiolarian ooze ; that the calcareo-siliceous earths 

 are similar to what is called by Prof. Haeckel " mixed Radiolarian 

 ooze " ; that some of the Foraminiferal earths are comparable 

 to Globigerina-ooze from 1000 fathoms, and that others greatly 

 resemble European Chalk; and, finally, that the coloured clays 

 bear a strong resemblance to the so-called " red clays " of modern 

 oceanic areas. Hence the raised Oceanic deposits of Barbados seem 

 to present us with an epitome of the various kinds of deposits which 

 are found on floors of warm seas at the present day. Equivalent 

 deposits are known in Trinidad and Jamaica ; and it is inferred by 

 the authors that the whole Central American and Caribbean region 

 was deeply submerged during the Pliocene period, leaving free com- 

 munication at that time between the Atlantic and Pacific Oceans. 



An Appendix by Mr. W. Hill treats of the minute structure of 

 the Oceanic earths and limestones and of the Foraminiferal muds 

 and detritial earths ; and this is supplemented by a Report from 

 Miss Raisin on the inorganic material of certain Barbados rocks. 



3. " ArchcBopneustes abruptus, a new Genus and Species of Echinoid 

 from the Oceanic Series in Barbados." By J. W. Gregory, Esq., 

 B.Sc, F.G.S. 



This genus belongs to a group of Echinoidea which has given 

 some trouble to systematists, owing to the union of the characters 

 of the ordei's Cassiduloidea and Spatangoidea ; the other genera 

 belonging to the group are Aster ostoma, Pseudasterostoma, and 

 Palceopneustes. The evidence of the new Echinoid throws light 

 upon the affinities of these genera. The main points suggested by 

 a study of the new species are : — (1) the abandonment of the name 

 Pseudasterostoma as a synonym of Palceopneustes : and (2) the inclu- 

 sion of the true Asterostoma, Palceopneustes, and ArcJiceopneustes in 

 the Adete Spatangoidea, whereby the Plesiospatangidae are left as 

 a moi'e homogeneous family, though bereft of the chief interest 

 assigned to it. 



A tabular summary of the nomenclature of the group is given. 



The best-known fossil species of Asterostoma and Palceopneustes 

 occur in Cuba, in deposits referred to the Cretaceous owing to the 

 resemblance of these Echinoids to the common Chalk Echinocorys 

 scutatus. The new genus includes a species from the same deposit, 

 which is probably of the same age as the Bissex Hill rock from 

 which the new species was obtained ; this is at the top of the Oceanic 

 Series, and belongs to the close of the great subsidence. 



