122 BULLETIN OF THE 
the arms are but little elevated, and have very broad bases ; they alternate regu- 
larly, and their borders are nearly or quite in contact. The three suckers next 
the mouth on each arm are nearly in one line ; the smaller inner ones forming 
a regular circle around the mouth. 
In the male, the right arm of the third pair is hectocotylized. This arm is 
decidedly shorter than its mate, and tapers much more rapidly to the tip, which 
is acute; along the posterior dorsal angle of the arm there is a strong, broad 
membranous fold, with the lower surface strongly concave, white, and crossed 
by numerous distinct transverse grooves ; the outer edge of the membrane is 
thin, sharp, white, and curves inward over the groove. The groove with its 
covering membrane extends close to the tip of the arm, where it terminates in a 
minute conical papilla; beyond this, there is a minute, conical, naked tip, but 
without any appearance of the spoon-shaped cavity and transverse grooves 
found in other species of Octopus. 
In alcoholic specimens the entire upper surface is usually very dark purplish 
brown, varying to dark bluish gray. In some specimens there are obscure 
patches of darker and lighter over the upper surface. In all the specimens 
examined there is a large, rounded, purplish black spot near the base of the 
web, and corresponding to the interval between the second and third pairs of 
arms. Lower surface of the body, head, and web much lighter than the upper 
surface, dull grayish or yellowish white, finely specked with purplish chro- 
matophores. Terminal portion of the siphon darker, much like the dorsal sur- 
face, inner surface of the web and arms grayish purple, paler than the upper 
surface. Inner surface and rim of the suckers yellowish white. 
The largest male observed (from San Diego, Cal.) has the dorsal arms 325 
and 390 mm. long, from the mouth; second pair of arms, 540 and 450 mm. 
long ; third pair of arms on left side, 550 mm.; right (hectocotylized) arm, 
400 mm. ; ventral arms, 500 and 490 mm.; greatest transverse diameter of the 
dorsal arms, 20 mm.; lateral arms, 25 mm.; ventral arms, 20 mm.; diameter 
of the larger suckers of the lateral arms, 11 to 14 mm.; of the twelfth sucker, 
15 to 16 mm.; breadth of the web between dorsal arms, from the mouth, 
60 mm.; between lateral arms, 70 to 100 mm.; between ventral arms, 60 mm.; 
length of body, 70 mm.; greatest breadth, 75 mm.; vertical thickness, 42 mm.; 
breadth of head across eyes, 45 mm.; breadth of dark spot at base of web, 
20 mm. 
A somewhat smaller male, with the tissues more contracted, has the dorsal 
arms 265 mm. long; second pair of arms, 270 mm. (probably reproduced) and 
280 mm.; third pair of arms, 300 mm. (left side); hectocotylized arm, 265 mm.; 
ventral arms, 285 mm.; diameter of the twelfth sucker of the lateral arms, 20 
to 22 mm.; of the adjacent suckers, 12 to 14 mm.; length of body, 70 mm.; 
breadth, 60 mm.; breadth of head, 45 mm. 
This species has an extensive southern distribution on the Pacific coast. It 
is common at San Diego, California, where it has been obtained by Dr. Edward 
Palmer and others. Numerous small specimens were obtained at Panama and 
on the coast of San Salvador by Mr. Frank H. Bradley, for the Museum of 
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