Records of Rare Hawaiian Decapod Crustacea 
Robert W. Hiatt 1 
Within the past year four crustaceans which 
are rare or previously unknown in Hawaii have 
been collected. Since these records are of im¬ 
portance to both taxonomists and students of 
animal distribution, it has been deemed worth 
while to make them available. The specimens 
are deposited in the collection of the University 
of Hawaii Marine Laboratory. 
Suborder NATANTIA 
Family Rhynchocinetidae 
Rhynchocinetes rigens Gordon 
Known previously only from the island of 
Madeira (Gordon, 1936: 76) and from Ber¬ 
muda (Burkenroad, 1939: 310; Gurney and 
Lebour, 1941: 113), this shrimp is found on and 
just off the reef on the south shore of the island 
of Oahu, Hawaiian Islands. This species, the 
only one of the six recognized members of the 
genus known to occur in the Atlantic, has not 
been found in the Pacific previously. Since it 
has been found in Hawaii, which is the eastern 
limit of the most widely distributed Indo- 
Pacific species, it is reasonable to suppose that 
it occurs in many other Pacific regions west of 
Hawaii, but thus far it has not been recorded. 
Perhaps the late discovery of this species in an 
area in which so much collecting has been done 
may be attributed to the fact that here, as in 
Bermuda, this species occurs as a sedentary, noc¬ 
turnal, littoral form and thus would not be eas¬ 
ily collected unless suitable collecting gear were 
used. The smallest Hawaiian specimens were 
taken with the aid of a light and a dip net; the 
larger ones were taken from a fine-meshed fish 
1 Department of Zoology and Entomology, Univer¬ 
sity of Hawaii. Manuscript received July 3, 1947. 
trap set in approximately 6 fathoms off Dia¬ 
mond Head, Oahu. One female specimen col¬ 
lected on February 19, 1947, was ovigerous. 
Hawaiian specimens ranged in length from 
55 to 115 millimeters compared to a range of 
from 80 to 97 millimeters for the specimens 
from Madeira. 
The vertical striae on the carapace are well 
developed in both sexes but are most conspicu¬ 
ous in the males. The third tooth behind the 
articulation of the rostrum is largest in all the 
Hawaiian specimens, as it is in the holotype. 
All Hawaiian specimens have 9 ventral teeth 
on the rostrum, whereas the holotype has 8. No 
significance may be attached to this feature, 
however, because the ventral teeth on the rostra 
of the paratypes vary from 7 to 11. The dorsal 
teeth of the rostrum are arranged similarly to ' 
those of the holotype. In the Hawaiian females 
the articulation of the rostrum extends less than 
half way to the strong lateral ridge, whereas in 
the holotype it extends almost to the ridge. In 
males from both localities the articulation ex¬ 
tends to the ridge. 
No significant differences were noted between 
the appendages of the holotype and those of the 
Hawaiian specimens except in the first pleopod 
of the females. The Hawaiian specimens have 
a broad, scale-like protuberance extending from 
the disto-lateral area of the protopodite as far 
as the basal one-fourth of the exopod. The lat¬ 
eral and distal margins of this protuberance are 
thickly clothed with setae. 
The branchial formula of Hawaiian speci¬ 
mens is identical with that of the Madeiran 
specimens, which differs from the branchial 
formula of R. typus M.-Edw. in that the arthro- 
branch corresponding to the fourth pereiopod 
C78] 
