190 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



While failing to see on what ground Dr. Frazer extended his conclu- 

 sions, based upon examination of a single locality in Cuba, to Jamaica, 

 Porto Rico, and the Windward Islands, it may be possible that some 

 of tlie rocks of the Sierra Maestra range of Cuba are of a Pre-Cretaceous 

 a^re, althou<>;h Kimball has shown that the diorites have overflown the 

 Tertiary. Personally, I have failed to find any Pre-Cretaceous crys- 

 tallines in the localities cited. 



Dr. W. Bergt has also strongly advocated the existence of an Archaean 

 plexus at the foundation of San Domingo,^ another of the Great 

 Antilles. Unfortunately, while his argument is strong, like Frazer's 

 it is largely hypothetical, and not founded upon extended field work. 

 The substance of his conclusions is as follows. 



Bergt had before him the following rocks from the southern and 

 southwestern parts of San Domingo : — Crystalline schists : horn- 

 blende gneiss ; pyroxene granulite ; fine-grained typical hornblende 

 schist ; chloritic hornblende schist, thin laminated, phyllite-like, folded ; 

 garnet amphibolite, augite-bearing, eclogite-like ; chloritic schist, etc. 



Older eruptive rocks : normal mica granites, having the appearance 

 both of mountain granite and vein granite ; protegene granites with the 

 most distinct evidences of pressure ; hornblende granites, even macro- 

 scopically so rich in large quartz grains that it is impossible to confound 

 them with syenite; syenite subordinate; diorite, quartz-diorite, " Blue- 

 beache"; diabase; quartz-diabase; picrite, olivine rock, serpentine. 



Younger eruptive rocks : basalts in doleritic, anamesitic, and basaltic 

 development, the latter compact and of the nature of a finely porous 

 lava ; andesites ; on the small island of Alta Vela also trachytes. 



He concludes that, " while according to Gabb, San Domingo forms 

 an exception, showing none but young eruptive rocks with very old^p- 

 pearance, the above series shows quite normally the well known petro- 

 graphic and geologic contrast betw^een older and younger eruptive rocks. 

 The eruptive rocks designated above as ' older ' differ plainl}' by their 

 state of preservation, by transpositions and new mineral formations, 

 from the volcanic rocks; they do not even resemble the transition rocks 

 distributed all over America (propylites, Andes diorites, etc.)." 



Bergt also concludes that the older eruptive rocks of San Domingo 

 are not the causes of the mountain movements, but, on the contrary, 

 were themselves subjected to such movements, and bear the traces of 



^ On tlie Geology of San Domingo, by Dr. W. Bergt. Sitzungsberichte und 

 Abliandlungen der naturwissenschaftlichen Gesellschaft Isis in Dresden, Jalirgang 

 1897, Juli bis December, Dresden, 1898, pp. 1-7. 



