ATLANTIC AND CARIBBEAN PYCNOGONIDA—HEDGPETH 17] 
dispersal for these forms gains some confirmation from a comparison 
of the pycnogonids from both sides of the Isthmus of Panama. Four- 
teen of the 20 genera known from the two regions (Cape Hatteras to 
about latitude 10° N. on the Atlantic side, Point Concepcién to the 
Galapagos on the Pacific side) are represented in both faunal provinces. 
Three species occur in both regions (the records for two of them 
antedate completion of the Panama Canal): 
Nymphopsis duodorsospinosa_. ‘Tortugas and South Carolina; Galipagos 
and Baja California. 
- Tanystylum calictrostre- - ~~ -- - Bermuda; Gulf of Panama. 
Pycnogonum reticulatum _ —-_--- Tortugas and Key West; El Salvador. 
There are also at least five pairs of closely related species, which 
may have become differentiated after the rising of the Isthmus: 
CARIBBEAN REGION PANAMIC REGION 
Callipallene 
emaciata* (Tortugas) californiensis (southern California) 
Ammothella 
rugulosa (Brazil, Bermuda, Tortugas) _—heterosetosa (GalA4pagos) 
Ascorhynchus 
armatus*t (Hatteras to Cuba) agassizi{ (Gulf of California) 
Eurycyde 
raphiaster (Tortugas) * longisetosa (Colombia) 
Tanystylum 
orbiculare*? (Brazil, Florida, Texas) duospinum (central California) 
tDeep-water species, possibly synonymous. 
* Also from east side of Atlantic. 
An interesting anomaly is the occurrence of species of Anoplodactylus 
with styliform probosces at Tortugas and the Hawaiian Islands. 
Although they are apparently not the same species, A. stylirosiris, 
new species (Tortugas), and A. intermedius Hilton are evidently 
closely related. 
WEST AFRICAN PYCNOGONIDS 
Unfortunately our knowledge of the west African pycnogonids is 
incomplete, and future collections from that region may convince 
another investigator that such species as Anoplodactylus polignaci 
and Hurycyde raphiaster owe their distribution to the influence of the 
westward-flowing North Equatorial Current rather than to the Gulf 
Stream. The richness of the Caribbean fauna indicates that it is a 
more favorable region for the development of species (as does the 
