42 
Fig. 2. Pinnixa transversalis (Milne Edwards and 
Lucas), male, station 783-38. A, right outer maxil- 
liped, X 20; B, abdomen, X 6; C, first pleopod, X 
26. Fringing hairs omitted. Drawn by Anker Petersen. 
faxoni meeting throughout their lengths; second, 
the male abdomen of the new species is more 
constricted in the central portion and more 
abruptly broadened distally than in P. faxoni 
(as shown in Rathbun’s figure 77a); third, the 
male first pleopods are different in the two spe- 
cies, the distal, spinelike process in P. faxoni 
being much longer, more slender, and bent at 
nearly a right angle to the axis of the append- 
age. Furthermore, P. faxoni is apparently the 
shaggier of the two species, but how much so 
cannot be determined because of the matting of 
the hairs in the type series of P. faxoni with 
fine silt. 
Pinnixa transversalis (Milne Edwards and 
Lucas) from the same locality (Fig. 2A-C) may 
be distinguished from the new species by the 
shape of the male abdomen, which is uncon- 
stricted medially and has a rounded terminal 
segment, by the external maxilliped, the pro- 
PACIFIC SCIENCE, Vol. XIV, January I960 
podus of which is less quadrate, and by the male 
first pleopod, which lacks the spinelike exten- 
sion with its bulbous base. The specimen from 
which these figures were made measures 4.8 mm. 
in length and 9.4 mm. in width and is without 
doubt the 5.0 X 9.4 mm. specimen, errone- 
ously recorded as a female (Garth, 1946: 498), 
of which measurements were given, since the 
female from the same station measures only 
3.3 X 6.8 mm. In addition, P. transversalis has 
a sharp ridge extending entirely across the pos- 
terior portion of the carapace, and the chelae in 
both sexes are narrow, thin, and straight, the 
fingers pointed. 
Finally, it should be stated that, while the 
specimens of Pinnixa transversalis were recov- 
ered from the arenaceous tubes of Chaetopterus , 
the commensal host of the new species remains 
a subject for future investigation. 
REFERENCES 
Darwin, Charles R. 1851. A Monograph on 
the Sub-Class Cirripedia . . . The Lepadidae; 
or, Pedunculated Cirripedes. xi + 400 pp., 1 1 
pis. Ray Society, London. 
1854. A Monograph on the Sub-Class 
Cirripedia . . . The Balanidae (or Sessile 
Cirripedes); the Verrucidae, &c. viii + 684 
pp., 31 pis. (col.). Ray Society, London. 
Garth, John S. 1946. Littoral brachyuran fauna 
of the Galapagos Archipelago. Allan Hancock 
Pacif. Exped. 5(10): 341-601, pis. 49-87. 
— 1957. Reports of the Lund University 
Chile Expedition 1948-49. No. 29. The Crus- 
tacea Decapoda Brachyura of Chile. Lunds 
Univ. Arsskrift., n. s., Avd. 2, Bd. 53(7): 
1-128, pis. 1-4, figs. 1-11. 
Milne Edwards, Henri, and Pierre H. Lucas. 
1842-44. IN Voyage dans 1’Amerique meri- 
dionale [Alcide d’Orbigny, ed.] 6(1): 1-39; 
9 [Atlas], pis. 1-17. P. Bertrand, Paris; V e 
Levrault, Strasbourg. 
Rathbun, Mary J. 1918. The grapsoid crabs 
of America. Bull. U. S. Nat. Mus. 97. xxii + 
461 pp., pis. 161, figs. 172. 
Verrill, Addison E. 1870. On the parasitic 
habits of Crustacea. Amer. Nat. 3: 239-250, 
figs. 41, 42. 
