=~ 
1871.] o7 
(Bland, 
Section IV. Puerto Rico with Vieque, the Virgin Islands, Sombrero, 
Anguilla, St. Martin, St. Bartholomew, and St. Croix. 
Puerto Rico, Vieque and the Virgin Islands, of which Anegada is the 
most eastern, stand on one and the same bank, an elevation of which to 
the extent of somewhat less than 40 fathoms (240 feet) would unite the 
whole, converting them into one Island. Sombrero is on another bank, 
about 40 miles from the Virgin bank, and 23 miles from the north end of 
the Anguilla bank. The depth of the channels which separate the Som- 
brero bank from the Virgin bank on the west, and the northern end of the 
Anguilla bank to the east, is not known, but soundings are recorded, at 
their margins, of 160 fathoms (950 feet) and 190 fathoms (1,140 feet), with- 
out bottom. 
Anguilla, St. Martin and St. Bartholomew stand on the western edge 
of another bank of considerable extent. Its southeastern end is 14 miles 
only from the Antigua bank, and the depth of water between the two is 
upwards of 122 fathoms (782 feet). An elevation of the Anguilla bank of 
about 40 fathoms (240 feet) would wnite the Islands upon it. 
The land shell fauna of the above named Islands is unquestionably the 
same ; it has some alliance with that of Haiti, but very little with that of 
the Islands to the south of the Anguilla bank. Not only is the absence 
of certain genera prevailing in Sections I., LE and, Ei, noticeable, kut 
the diminished number of representatives of others is equally so, for 
example: 
in § I. Sill: Sty. 
MM GBRIGMaStOMA ee erst oe cere ers, 13 species, 1 3 
AlCa0iia sya ea eee 9 os 2 il 
Strophia... sco .5 ve pie OR ue Ste. oe Cae a 2 2 
Mactocoramins cia, asd fos io 8 ee 85 £6 ak) 2 
(Oh dinotclill Ey OW ees eee eee 93 fer eeG 6 
The fact that Megalomastoma, Aleadia, Strophia, and Macroceramus are 
not represented in the Islands south of the Anguilla bank (§ V.) and that 
in those Islands there are 4 species only of Cy lindrella, affords striking 
proof of the difference of their faunas. 
St. Croix is not unfrequently classed with the Virgin Islands, from 
which it is 35 miles distant, but it stands on a bank disconnected from 
any others and with very deep water around it. Soundings are on record 
(taken, I believe, by Capt. Parsons, R. N,), between it and the Virgin 
bank, about the mid-channel, of 1,550 fathoms (9,300 feet), and not far 
from its northern shore of 2,000 fathoms (12,000 feet), without bottom being 
found. 
The following soundings to the eastward were obtained by the U. §. 
8. Yantic, in 1870, between St. Thomas and Saba: 
fathoms. feet. 
N. Lat. 18° 01/ 50", W. Long. 64° 10/ 20/7.—1,825 = 10,950 
uy 7° 55/ 00’, “ 68° 50’ 30/.—1,240 — 7,440 
Ay Es §.—-VOh, el 
