502 
PACIFIC SCIENCE, Vol. XXII, October 1968 
Formal Description 
TYPE locality: East of south end of Isabela 
Island, Galapagos. 
MALE HOLOTYPE: Head (Fig. 6b) lobes mod- 
erately produced and obtuse, eyes round. Body 
delicate, length from anterior margin of cephalo- 
some to tip of telson 3.8 mm (paratypes 
3. 0-3. 8 mm). Peraeon segments 3-6 (Fig. 2f) 
each with a very long, slender spine on its 
ventral surface, those of segments 3 and 4 
curved forward, and those of segments 5 and 
6 slightly recurved. Antennules slightly over 
half the body length, the first peduncular seg- 
ment slightly shorter than the second, the third 
about the length of the second; flagellum 
slightly longer than the peduncle, 12-segmented 
on one side, 11-segmented on the other (para- 
types with a maximum of 13 segments); acces- 
sory flagellum 3-segmented, the third segment 
rudimentary. Antenna about % the length of the 
antennule, the fourth and fifth peduncular 
segments subequal; flagellum 4-segmented on 
one side, 5 -segmented on the other. Peraeopod 
1 (Fig. 2a) with the coxopodite produced 
anteriorly, rounded; basipodite expanded antero- 
proximally; meropodite short; carpopodite oval, 
longer than broad, with a median dentiform 
process on the anterior margin, and at the pos- 
terior distal angle, a short stout tooth, basal to 
which, on the posterior margin, is another small 
tooth. Propopodite over half the length of the 
carpopodite, the palmar angle produced into a 
forward projecting, blunt tooth, opposable with 
the dactylopodite, which is of moderate length 
and has accessory teeth on the distal part of the 
inner margin. The posterior margins of the 
meropodite, carpopodite, and propopodite 
densely setose, the setae exceptionally long, 
being about 0.5 mm, 0.4 mm, and 0.3 mm on 
each podomere respectively. Peraeopod 2 (Fig. 
2e) with the basipodite moderately expanded, 
the anterior margin slightly concave; carpopo- 
dite and propopodite subequal in length and 
Fig. 3. Acuminodeutopus heteruropus Barnard, playa blanca, costa rica. $ : b, head and peraeopod 
1; c, peraeopod 2. $ : a, peraeopod 1; d, peraeopod 2. 
