Geology and Mineralogy. 227 



3 have a width of two to four miles, and 2 of 2\ to 4 miles. 

 There is also a hill (Drews Hill) of trachydoleryte near the cen- 

 tral line of the island which is spoken of as a volcanic hill. The 

 Lower marine limestone contains shells and fossil corals. Among 

 the corals Prof. Duncan identified Alveopora dcedalea and IStylo- 

 ■ccenea lobato-rotundata Mich., the latter a species occurring in the 

 lower limestone of Malta and elsewhere, and Mr. Purves adds 

 Prionastrwa diversiformis Mich., Solenastroea Turonensis Mich., 

 Porites Gollegnana Mich., all Miocene species. The Alveopora 

 is a living Red Sea species. Orbitoides Mantelli, recognized by- 

 Prof. T. Rupert Jones from the chert of Antigua, Mr. Purves 

 found in the upper limestone and not in the marine chert ; and he 

 adds that this foraminifer ranges from the beds of San Fernando 

 of Trinidad, referred to the Eocene, to the summit of the Miocene 

 of Jamaica. 



The freshwater chert contains species of Melania, Zonites, 

 Nematura or Amnicola, Planorbis, Melampus, Neritina, Trunca- 

 tella, Pomatias? Of these eight genera, the first three, the 6th 

 and the 8th, are not now represented in Antigua ; and the species 

 of Planorbis, Melampus and Truncatella cannot be identified 

 with those now existing there. The genus Zonites is unknown in 

 the Antilles and all Central America ; and Melania occurs in 

 Cuba but not in the Antilles. A remarkable fact is the faithful 

 reproduction, by the silica, not only of the shells, but in certain 

 cases, of parts of the animal itself, especially in specimens of 

 Melania, and, less well, in those of Zonites, Melampus and Nema- 

 tura. 



The shells and corals of the upper limestone and marls have 

 been referred to the Miocene by Prof. Duncan. The fossil corals 

 are to a large extent silicified ; and, besides, the beds contain 

 large geodes, made probably through the removal of corals ; but 

 the limestone remains unsilicified. The silica is referred to the 

 waters of hot springs. 



The recent horizontal marls, which make a terrace along the 

 northeast coast, contain recent terrestrial shells. But two of 

 them, species of Succinea and Helicina, are not now found in the 

 island. No human remains have been discovered in the beds. 



The papers by Prof. Duncan referred to are in the Quart. J. 

 Geol. Soc, xx, 411, 1863, and xxix, 562, 1873, Geol. Mag., i, 97, 

 101, 1864 ; by Prof. T. R. Jones, Geol. Mag. i, 102, 1864. 



5. Pennsylvania Geological Survey. — The following volumes, 

 reports of the progress of the survey, have been recently issued: 



No. C 6 . Field Notes in Delaware County ; by C. E. Hull, with 

 a colored geological map of the county, five engraved colored 

 plates, and thirty-nine photographic views of the Granite Quarries, 

 Kaolin Mines, Serpentine outcrops, and the Castle Rocks. Pub- 

 lished in advance of the Geological Report on the County, Part 2, 

 by J. P. Lesley. 128 pp. 8vo. Harrisburg, 1885. 



No. RR. Township Geology of Elk and Forest Counties, by 

 C. A. Ashbuener ; of Cameron County, by A. W. Sheafek. 

 404 pp. 8vo, 1885. 



