194 . MR. JTJKES-BEOWNE AND PROF. HARRISON 



Barbadian earths with those obtained from the modern ooze, and 

 found that about 25 per cent, of the Barbadian forms are known 

 from the modern ooze. It is true that, as Mr. Gregory points out, the 

 living radiolaria have not been so well investigated that such a 

 comparison can be taken as having the value that it would have in 

 the case of one of the higher groups ; still the fact remains that 

 many of the Barbadian species are absent from the recent deposits, 

 and therefore, so far as the radiolarian evidence goes, it points to a 

 date somewhat older than Pleistocene or post-Tertiary ; a Pliocene 

 date would be entirely in accord with this evidence. 



[As regards the diatoms, we have not been able to ascertain 

 whether any of them are extinct species or bear in any way on 

 the question of geological age, but in the recently published volume 

 on Deep-sea Deposits (' Challenger ' Expedition Series) Dr. J. Mur- 

 ray furnishes us with a strong point of comparison with modern 

 abyssal deposits. Fragments of the frustules of the diatom Ethmo- 

 discus are frequently present in the radiolarian earths of Barbados 

 in considerable quantity, and he remarks that this is " quite charac- 

 teristic of some of the deepest tropical red clays and radiolarian 

 oozes far from land " {op. cit. p. 31).— Feb. 16th, 1892.] 



The most important fossil which has yet been obtained from the 

 radiolarian beds is the echinoderm which was described by Mr. J. 

 W. Gregory in 1889 under the name of Cystechinus crassus} We 

 have ascertained that the well at Haynesfield, from which this 

 fossil was obtained, had a depth of about 168 feet, 140 of this being 

 coral-rock, and the remainder radiolarian earth ; the specimen came 

 from near the bottom at a depth of about 166 feet, as stated in 

 Mr. Gregory's paper. The occurrence of this echinoderm is of 

 great importance, inasmuch as it affords valuable evidence both as 

 to depth of water and geological age. 



Mr. Gregory remarks that " Cystechinus is one of the most typical 

 of deep-sea echinoids ; thus, for example, Neumayr quotes it with a 

 few other genera as never found above the 1000-fathom line." 

 Three species of Cystecliinus were obtained during the ' Challenger ' 

 Expedition, all of which came from very deep water. "C. clypeatus, 

 the species which is probably the nearest ally of C. crassus, was 

 found off' Tristan da Cunha at Stations 133 and 3;34, and in the 

 China Sea at Station 205, at depths of 1900, 1915, and 1050 fathoms 

 respectively." 



No fossil form of the genus was known previous to the discovery 

 of Cystecliinus crassus in Barbados, so that its presence gives little 

 assistance in determining the age of the deposit. Since many of 

 the modern oceanic echinoderms belong to very ancient types, we 

 might expect Cystechinus to be present in oceanic deposits belonging 

 to any Tertiary period. 



The only other fossil which has been obtained from the radiolarian 

 beds is a shark's tooth of the Larana type ; this is in the possession 

 of Mr. Armstrong, of Little Island estate, Barbados, and is embedded 

 in a fragment of the grey limestone of Bissex Hill. 

 ^ Quart. Journ. Geol. Soc. vol. xlv. p. 640. 



