226 THE GEOLOGY OF BAEBADOS. 



group as the Hexactinellida has afforded one instance of a compara- 

 tively shallow-water species, Cystispongia superstes having been 

 dredged from 18 fathoms off Yucatan. 



Prof. Harrison pointed out, in answer to Dr. Blauford's remarks, 

 that the evidence upon which the red and mottled argillaceous earths 

 of the Oceanic Series were considered by Mr, Jukes-Browne and 

 himself to be deep-sea deposits was the close resemblance in physical 

 properties and chemical composition which they present to certain 

 of the modern deep-sea oozes which have been termed ' red clays,' 

 and that the only organisms found in them were purely siliceous, 

 being principally the remains of radiolaria with a few sponge-, 

 spicules. The ' clay ' occurring in the pure radiolarian marls was 

 also separated, and upon comparison was found to be similar to the 

 argillaceous earths. The term ' red clay ' appears to have been 

 used in the ' Challenger ' Expedition JReports in a very comprehen- 

 sive manner, as under it are included not only argillaceous deposits 

 containing but few organisms, but also deposits consisting in some 

 cases of radiolarian, and in others of foraminiferal organisms. 



Mr. J. W. Gregory remarked that, as the new eehinoid occurred 

 in a limestone at the extreme top of the Oceanic Series, it in no way 

 disproved the deep-sea origin of the radiolarian marls. He fully 

 agreed with Dr. Blanford in doubting any considerable submergence 

 of the Isthmus of Panama in Upper Cainozoic time ; Dr. Maack's 

 collection proved only an Eocene or Miocene submergence, and the 

 surveys of Lieut. Wyse and the French engineers of the Canal had 

 not revealed any considerable elevation of the recent marine deposits. 

 He exhibited specimens of radiolarian marls from Cuba, which were 

 identical in characters, variation, and mode of occurrence with 

 those of Barbados, and he maintained that this completed the 

 Authors' case, and disproved the objection that had been advanced 

 that these deep-sea deposits only occurred on the margin of a 

 volcanic area. 



Mr. W. Hill drew attention to the contents of the calcareous 

 earths and their resemblance to modern chalky oozes. 



