44 



bulletin: museum of comparative zoology. 



" Trappean Series," " Cretaceous Limestone," and " Yellow Limestone " 

 (as used for the western parishes). 



While it is still impossible completely to differentiate all the beds of 

 the Blue Mountain Series, our observations have enabled us to make 

 a more accurate classification of them than any hitherto presented, 

 which may be stated as follows : — 



Upper Division 

 (Eocene) 



Blue Mountain Series - 



Richmond Beds. 



Lower Division 



Minho 



Beds. 



(Upper Cretaceous) Ballard 



Logic Green 

 Frankenfield 

 Jerusalem 

 Yallahs 



The Basement Beds. — The chief difficulty of classification is the com- 

 plex folding and partial concealment which make it impossible to deter- 

 mine the exact base of the series. The Jamaican Reports present 

 conflicting conclusions on this subject, inconsistently stating in different 

 places that the base of the section is composed of igneous rocks, Creta- 

 ceous limestones, and a formation termed the " Metamorphosed Series." 



From the tabulations, especially that given on the last page of the 

 Reports, one infers that its authors believed the base of the Jamaican 

 section was crystalline and overlain by the so called " Metamorphosed 

 Series ^' beneath the limestones with Cretaceous fossils, but a careful 

 perusal of the Reports does not justifj' this interpretation. In numerous 

 places throughout the text of the work the intrusive nature of the 

 igneous rocks into the beds of the Blue Mountain Series is noted, as 

 further recorded in the portion of our report treating of the igneous 

 rocks. Sawkins ^ expresses doubt as to the propriety of drawing a dis- 

 tinction between the Cretaceous and the so called "Metamorphosed 

 Series," and clearly states that the latter " comprises strata of the 

 Cretaceous and conj^lomerate formations which have experienced a change 

 of structure due to the intrusion of igneous rocks." ^ In view of this 

 fact, as verified by our own observations, the so called " Metamorphosed 

 Series," as a structural formation, may be dismissed from consideration. 



There may be doubt as to whether the oldest rocks are Cretaceous 

 limestone, whicli Etheridge asserts" ** is clearly at the base of the series," 



1 Jamaican Reports, p. 65. 



- Ibid., p. 47. 



8 Ibid., p. 308. 



