214 THE VOYAGE OF H.M.S. CHALLENGER. 



and is peculiar to Fernando Noronha, its nearest ally, Euprepes maculatus, inhabiting 

 Demerara; it is very abundant on the main island, and especially so on Mount St. 

 Michael, where it is remarkably tame ; some specimens are more than a foot in 

 length. Rev. 0. P. Cambridge says that two spiders from Mount St. Michael are Argiope 

 argentata, Latr., and Neon sp. A new species of Lepidoptera (Catochrysops trifracta, 

 Butler) was caught on Rat Island ; it is interesting as being of a Malayan type. 1 



The rock at Rat Island is nepheline-basalt. In the southeast part of this island 

 there is a tufa composed of carbonate of lime and of clastic grains of organic and mineral 

 origin. The grains are rounded, and each is bordered with a little zone of calcite ; the 

 mineral particles are olivine, basalt, and palagonite. The rock of Platform Island is a 

 felspathic basalt. 



Professor Thomson and Mr. Murray dredged during the day in the steam pinnace 

 in depths varying from 7 to 25 fathoms. The bottom was covered with a calcareous 

 sand or gravel, of a mottled red and white colour, the fragments varying from 2 to 3 cm. 

 in diameter, and consisting chiefly of calcareous Algae with fragments of Echinoderms, 

 Molluscs, Polyzoa, Corals, Polytrema, Amphistegina, and other Foraminifera. 



Fernando Noronha to Bahia. 



On the 3rd September, at 9.30 a.m., the ship left Fernando Noronha for Bahia, 

 carrying a line of soundings to the westward to the depth of over 2000 fathoms (see 

 Sheet 14). 



During the passage to Bahia the wind for the first few days hung well to the south- 

 ward, the average direction being S.S.E., force 4 to 5, squally, with passing showers; 

 after passing the parallel of 8° S. it fell light and came more from the eastward. 



In consequence of the trade wind being so far to the southward the ship approached 

 the American coast on the 6th parallel, and then steamed along the land to Bahia, 

 keeping at such distances from the shore as seemed suitable for sounding or dredging, 

 and taking advantage of any slant of wind to economise fuel. Several whales were seen 

 on the course southward. 



On the 6th September, at Station 117, the Barrieras do Inferno could just be dis- 

 tinguished from the deck at a distance of 27 miles. From Station 117a, where the 

 depth was 500 fathoms, and the distance from the shore 16 miles, the land could be 

 plainly seen, but there were no objects sufficiently prominent to fix the position of the 

 sounding by bearings. Later on the same day a cast was taken in 18 fathoms, 9 miles east 

 of Point Moleque, with the right extremity of the Barrieras do Inferno N. 42° W. (true), 



1 In Mr Butler's paper {Ann. and Mag. Nat. Hist, ser 5, vol. xiii. p. 195, 1884) this species is accidentally stated 

 to be from " Rat Island, Straits of Malacca." 



