MUSEUM OF COMPARATIVE ZOOLOGY. 299 
Everything either remains at a short distance below the surface, or is 
blown out to seaward of the islands. The phosphorescence, in conse- 
quence, is far less brilliant than in the Gulf of Mexico, although occa- 
sionally the masses of Ctenophore (a species of Mnemiopsis), swimming 
at different depths, produced a very striking illumination: sudden 
flashes of light suddenly appearing as if coming from great balls of fire 
floating a short distance below the surface. The most striking phospho- 
rescent phenomena were produced by a small Annelid, allied to Syllis, 
which moved over the surface of the water with great rapidity, per 
forming the most remarkable gyrations, and tracing its path, which 
remained phosphorescent for a short time, by a brilliant line of light. 
Among the deep-water forms, several of the species of Gorgonis and 
Anthipates (especially Riisea) showed a bright bluish phosphorescence 
when coming up in the trawl. One Ophiuran also, like one of the Med- 
iterranean species mentioned by Panceri, was exceedingly phospho- 
rescent, emitting along the whole length of its arms at the joints a 
brilliant, bluish-green light. 
One of the most interesting results reached by this year's cruise is 
the light thrown upon the former extension of the South American 
Continent, by the soundings taken while dredging, and those subse- 
quently made in the passages between the islands by Commander Bart- 
lett. 'Phese, together with the soundings already known, enable us to 
trace the outline of the old continent with tolerable accuracy, and thus 
obtain some intelligible, and at the same time trustworthy, explanation 
of the peculiar geographical distribution of the fauna and flora of the 
West India Islands. As is well known, Cuba, the Bahamas, Hayti, 
and Porto Rico, instead of showing, as we might naturally assume from 
their present proximity to Florida, a decided affinity in their fauna and 
flora with that of the Southern United States, show, on the contrary, 
unmistakable association with that of Mexico, Honduras, and Central 
America; the Caribbean Islands show in part the same relationship, 
though the affinity to the Venezuelan and Brazilian fauna and flora is 
much more marked. 
In attempting to reconstruct, from the soundings,* the state of things 
existing in a former period, we are at once struck by the fact that the 
Virgin Islands are the outcropping of an extensive bank. The greatest 
depth between these islands is less than 40 fathoms, this same depth 
being found on the bank to the east of Porto Rico, the 100-fathom line 
* See the maps aecompanying this letter, for which I am indebted to the Hon. 
Carlile P. Patterson, Supt. U, S. Coast Survey. 
