170 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 97 
It is more reasonable to assume that such species have migrated 
as adults on the sargassum or as larvae in hydroids on the sargassum 
or in the medusa stage of the hydroid host. Timmermann (1932), 
in his study of the fauna of the pelagic sargassum, discovered that 
two pycnogonids, Hndeis spinosa and Anoplodactylus petiolatus, are 
apparently characteristic elements of this fauna, and Hodgson (1915) 
vaguely described another species, Anoplodactylus maritimus, from 
sargassum south of the Azores. Recently I have taken Tanystylum 
orbiculare from sargassum cast ashore on the Gulf coast of Texas. 
(Fig. 8.) 
The fact that Hndeis spinosa is common in the Tortugas region (it 
has also been found on the coast of South Carolina, in Chesapeake 
Bay, and at Bermuda) supports Timmermann’s tentative suggestion 
that it might be an American species that owes its wide distribution 
along the coast of Europe to its pelagic habit. The apparent scarcity 
of Anoplodactylus petiolatus on the American side of the Atlantic 
would seem to contradict this explanation, especially since it is more 
common on the sargassum in mid-Atlantic than EHndeis spinosa. 
However, it has been collected from sargassum on the Texas coast, 
while Endeis spinosa is yet to be collected from that part of the Gulf 
of Mexico. Nevertheless, Endeis spinosa is widely spread along the 
American Atlantic coast, from Brazil to Woods Hole, including the 
Panama region. It is possible that Giltay’s Anoplodactylus parvus 
is the same species as A. petiolatus, in which case the American range 
of A. petiolatus would include Chesapeake Bay and Bermuda. 
In addition to the two pycnogonids of known pelagic occurrence, 
at least eleven species are found on both sides of the Atlantic, exclusive 
of the Boreal-Arctic species, which have a more continuous distribution. 
Seven of these are found in the Tortugas-Key West region alone. It 
will be noted, from table 3, that two species, Ammothella appendiculata 
and Endeis charybdaea, have been found on the coast of southern 
Brazil but are not represented in the Tortugas collections. Their 
absence from the Florida Keys cannot be presumed from available 
evidence, and two species described from Brazil have been found 
in the area. It is probable that southern Brazil is the meeting place 
of the American tropical and the Magellanic faunas.® 
The distribution of these species, several of them collected at the 
surface, appears to represent a dispersion from the rich Caribbean 
fauna rather than a concentration of widely scattered elements in 
that region. On the other hand, the Mediterranean fauna might be 
considered a concentration of European Boreal types and American 
Subtropical forms. The possibility that the Caribbean is a center of 
8 Larval stages of Anoplodactylus petiolatus have been found in medusae by Lebour (1916 and 1945). 
9 Only two isolated collections from the equatorial coast of eastern South America have been recorded in 
the literature: Pentapycnon geayi Bouvier (French Guiana) and Nymphopsis anarthra Loman (Venezuela). 
