498 PROF. J. W. SPEirCEB OJ^ THE GEOLOGICAL AND [NoV. IQOI, 



From these considerations Duncan inferred that the formation 

 belonged to the mid-Tertiary or Miocene Period. 



It has been stated before (p. 495) that Prof. Rupert Jones had 

 found an Orhitoides Mantelli in the Nugent Collection. I also found 

 a species of Orhitoides in the marls of Wetherell Point. This fossil 

 is one of the most important collected, as it affords a correlation 

 with the Tertiary of the South-eastern States, and would suggest 

 that the formation is somewhat older than the mid-Tertiary 

 Period, in a word, that the rocks are older Miocene or Oligocene. 

 Thus it would appear that the time of this formation was a con- 

 tinuation of that of the fossiliferous beds of the tufaceous deposits 

 (reaching probably to a thickness of several thousand feet) — the 

 whole being one undivided geological unit, referable to the older 

 Tertiary Period (including the Eocene and extending to the later 

 Oligocene days),^ 



The shells of the same formation, which, as before stated, are 

 mostly in the form of casts, have not been determined, but 

 Prof. W. H. Dall, having cursorily examined them, formed a 

 general impression confirmatory of the evidence established by 

 the corals. 



Prof. Gregory "-^ mentions EcMnanthus (or Diplothecanthus of 

 Duncan) concavus, Cott. and E. Antillarum, Cott., sent by Mr. 

 Eorrest, as the first echinoids recorded as coming from Antigua, thus 

 correlating the beds of this island with those of St. Bartholomew. 



The eroded surfaces of these limestones give form to the hills, 

 rising to 200 or 350 feet (one point to 456 feet) above the sea, 

 with the gently sloping depressions between them. The higher 

 portions of the hills appear not to have been subsequently covered 

 by the accumulations about to be described. But the question of 

 the erosion-features produced during the different periods since 

 the early Miocene emergence of the limestones will be considered 

 as a separate topic. I have refrained from comparing the age 

 of the rock-formations and other features with their equivalents 

 in the other West Indian islands, as this subject should form a 

 chapter by itself. 



The series has become a type in the Antillean islands, and may 

 thus appropriately be called the Antigua formation. 



YII. The Hodge's Hill Sandstones. 



Hodge's Hill is situated at the north-eastern angle of Antigua, 

 rising to a height of 154 feet above the sea. The exposed strata 

 of this hill are composed of a creamy white calcareous sandstone. 

 It is compact and suitable for building-material, hardening and 

 darkening on exposure. The dip is in the normal north-easterly 

 direction, but less than that of the White Limestones — not ex- 

 ceeding 10°. The rounded grains of calcareous sand give the 



•^ [Since I sent in the manuscript of this paper, Dr. Vaughan has shown that 

 the Antiguan coral-fauna is identical with that of the lower beds of the Upper 

 Oligocene formation in South-western Geoi-gia. See ' Science ' n.s. vol. xii (1900) 

 pp. 873-75.] 



2 Quart. Journ. Geol. Soc. vol. li (1895) p. 295. 



