902 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Penaeus marginatus Randall. 
(PL xix, fig. 2. ) 
Penceus canaliculatus Randall, Jour. Acad. Nat. Sci. Phila., VIII, 1839 (1840), 146 (part). 
Penceus marginatus Randall, loc. cit. (part). 
Notes on the type specimens. — In the museum of the Philadelphia Academy of Natural Sciences are 
eight specimens labeled 1 ‘ Peneus canaliculatus Oliv. , Sandwich Islands, N uttall and Townsend. ’ ’ These 
were doubtfully named “ canaliculatus ” by Randall, therefore he suggested in print at the same time 
“ marginatus ” in case the species should prove to be new. The specimens are now in very bad con- 
dition, and have never been carefully examined. There are two species represented— five specimens 
of the true P. canaliculatus (Olivier), and three specimens which it seems proper to consider the types 
of P. marginatus Randall. All are half grown. 
In the specimens of the well-known P. canaliculatus, the median ridge of the carapace is deeply 
grooved. The distance behind its posterior spine is from one and three-fourths to one and four-fifths 
times the distance in front of it measured to the posterior margin 
of the orbit. Only one individual now has a complete rostrum; 
its teeth are 9/1. 
- In the three examples of P. marginatus the median ridge is not 
grooved; the distance behind its posterior spine is one and two- 
thirds times the distance from the spine to the orbit. Two speci- 
mens have the rostrum intact, with 10/2 teeth. 
Description of mature specimens in the V. S. National Museum : 
Size and general appearance same as that of P. canaliculatus. Dorsal 
crest 9-10 toothed, inferior rostral teeth 2-3. • Dorsal keel con- 
tinued nearly to posterior margin pf carapace, itself not grooved, 
but bordered on either side by a broad furrow which extends pos- 
teriorly as far as the keel. Flagella of antennulse as long or nearly 
as long as peduncle. Pereiopoda and abdomen much as in 
P. canaliculatus. 
Petasma and thelycum similar to those of P. ashiaka Kish- 
inouye and P. monodon Fabricius, the longitudinal median fissure 
of the latter bordered on either side by the much-thickened inner 
margin of the lateral plate. 
Dimensions of largest specimen, a female, station 3857, 163 mm. 
Description of. young specimens. — Specimens 40 mm. in length and 
smaller, were taken in numerous hauls of the surface net. They 
are relatively slenderer than the more adult; the median carina 
and lateral grooves fade out before reaching as far back as in the 
adult, that is to say, about half way between the gastric spine and the posterior margin; the antennal 
scale is longer; the fourth abdominal segment is noncarinate, the sixth is noticeably longer than in 
the adult, the telson is armed close behind the small spines of the third pair with a pair of long spines. 
The color of this form is said to be French blue, and traces of it remain in the alcoholic specimens. 
It is possible that I am mistaken in attributing this young form to P. marginatus, but the general 
make-up, the rostral formula, and the probability of the existence of the young of that species in so 
large a collection, all tend to prove their identity. 
Distribution.— The large and mature specimens are found only in deep water; medium and smallish 
specimens are restricted to shallow water along shore, while the very young occur at the surface. 
Specimens 125 mm. and upward in length. — South coast of Molokai Island, 153 to 142 fathoms, 
station 3832; Pailolo Channel, 122 to 141 fathoms, stations 3857, 3858, 3897, 4102, and 4103. Vicinity 
of Laysan, 173 to 182 fathoms, station 3958; north coast of Maui, 45 to 52 fathoms, station 4070. 
Specimens 40 to 95 mm. in length. — Honolulu, 1901; Pearl Harbor, April 23, 1902; Honolulu market, 
1902; Hanalei, Kauai, June 23, 1902; Kaunakaki Harbor, Molokai, shallow water, station 3844; Hilo, 
Hawaii, 1901; Hilo, Hawaii, H. W. Henshaw. 
Specimens 40 mm. and under in length.— Between Erben Bank and Kaiwi Channel, surface, station 
Fig. 55 .—Penxus mar ginatus . a, 
Petasma, ventral view, station 3832, 
X 4. 6, Same, side view, x 4£. c, 
Thelycum, station 4070, x 3i. 
