Pinnixa darwini , a New Species of Pinnotherid Crustacean 
from the Galapagos Islands 
John S. Garth 1 
While REPORTING on the Crustacea Decapoda 
Brachyura of the Lund University Chile Expedi- 
tion (Garth, 1957), the writer had occasion to 
review the status of the genus Pinnixa White 
on the west coast of South America, and, par- 
ticularly, to re-examine specimens previously 
referred by various authors to P. transversalis 
(Milne Edwards and Lucas, 1842: pi. 10, figs. 3, 
3a-e; 1844: 23). This proved to be a quasi- 
generic designation, or at least a species complex 
under which two or more valid species had been 
masquerading. It is not surprising, therefore, 
that when specimens from Darwin Bay, Galapa- 
gos Islands, so reported by the writer (Garth, 
1946: 497), together with certain other Gala- 
pagos material more recently acquired, came 
under the same close scrutiny, it was discovered 
that in addition to the aforementioned P. trans- 
versalis, which has as its type locality the shores 
of Chile, a new and perhaps endemic species 
was represented among them. It being deemed 
inappropriate to include a Galapagos Islands 
species in a report on the fauna of Chile, its de- 
scription was withheld at the time and is now 
presented in connection with the world-wide 
observance of the Darwin Centennial, the 100th 
anniversary of the publication in 1859 of "The 
Origin of Species.” 
Although Charles Darwin is not known to 
have collected decapod crustaceans in the Gala- 
pagos Islands, or elsewhere along the west coast 
of South America, during the celebrated voyage 
of the Beagle, his monograph on the Cirripedia 
(1851-1854) was a fundamental contribution to 
crustacean systematics. Had his genius for eluci- 
dating the obscure been directed toward the 
crabs instead of toward the barnacles, our pres- 
ent knowledge of the Pinnotheridae, a family of 
brachyurans living as commensals with poly- 
1 Allan Hancock Foundation, University of South- 
ern California, Los Angeles, California. Manuscript 
received September 5, 1958. 
chaetes, mollusks, and echinoderms, would have 
been immeasurably enriched. The revelation of 
their fascinating habits was left to a later group 
of nineteenth century investigators, notably Ver- 
rill (1870), who referred to them quaintly, al- 
though not too correctly, as parasites. However, 
in view of Darwin’s contribution to systematic 
carcinology and to Galapagan zoogeography, it 
seems entirely appropriate that a new species of 
pinnotherid crustacean from the bay that bears 
his name and the islands to which he brought 
lasting fame should be dedicated to the illus- 
trious proponent of evolutionary theory and ex- 
ponent of natural selection. 
Family PINNOTHERIDAE Dana 
Genus Pinnixa White 
Pinnixa darwini , n. sp. 
Fig. 1A-F 
TYPE: Male holotype and ovigerous female 
allotype, A.H.F. No. 3812a and b, respectively, 
from Darwin Bay, Tower Island, Galapagos 
Islands, 40-70 fathoms, January 16, 1938, col- 
lected by the "Velero III” at station 783-38. 
Male paratype, same locality, date, and station 
number, to be deposited in the collections of 
the U. S. National Museum. 
MEASUREMENTS: Male holotype, length 3.1 
mm., width 5.8 mm., frontal width 0.9 
mm., fronto-orbital width 2.15 mm., cheliped 
(ischium-merus-carpus 1.6 mm., manus-dactylus 
3.0 mm.) 4.6 mm., chela 3.0 mm., superior mar- 
gin 1.8 mm., height of palm 1.6 mm., dactyl 
1.5 mm., merus of leg three: length 2.8 mm., 
width 1.2 mm. Female allotype, length 3.8 mm., 
width 8.2 mm. 
diagnosis : Cardiac ridge obsolescent; antero- 
lateral margins forming a sharp, milled crest. 
Eyes and eyestalks large, filling orbits. Propodus 
of external maxillipeds short and broad, dac- 
tylus considerably longer. Chelae moderately 
robust, fingers enclosing an oval gape. Merus of 
39 
