106 University of California Publications in Zoology (Vou. 28 
none; cervical groove, 2, 2, 1, 2. Otherwise the principal spines of the carapace 
are situated as follows: subdorsal or branchial ridge, five; one on branchial area 
between median and branchial carinae; lateral carina, running from external angle 
of the orbit to the posterior margin of the carapace, with sixteen spines arranged 
six-three-seven, of which the last four are the largest; upper of two ridges, below 
the lateral carina, running from the outer side of the base of the antenna almost 
to the hinder border of the carapace, spinulose along the anterior third of its 
course; the lower ridge, beginning on the margin of the pterygostomian region, 
one-third of the way from the anterior end of the carapace and curving outward 
and backward to the posterior margin of the carapace, with five spines which 
decrease in length from the first to the fifth, followed by small denticles; the 
anterior spines in this last series are the largest on the body. 
Eyes rudimentary, without corneae; eyestalks consisting of a large lobe, 
immovably fixed in a deep sinus in the anterior border of the carapace. This 
lobe sends forth an elongated, cylindrical process, directed outward and down- 
ward below the antero-lateral angle of the carapace; the anterior margin of the 
lobe bears a prominent papilla, or tubercle. 
Abdomen with five longitudinal rows of spines, one median and two pairs of 
lateral; median row with one spine on the first abdominal somite, one or two on 
the second, two or one on the third, two or three on the fourth, two on the fifth, 
one on the sixth, and two on the base of the telson. 
Dimensions.—Type, male: length from rostrum to end of telson 62.5 mm., of 
carapace 34.5 mm., of abdomen 30 mm.; specimen taken off California by the 
‘¢ Albatross’’: length from rostrum to end of telson 75 mm. 
Color—Of Faxon’s specimens in life, ‘‘purplish red, the branchial regions 
livid.’’ California specimen: ‘‘extremities shaded with pale rose, body parts 
flesh color.’’ 
Type Locality——Off Malpelo Island, vicinity Gulf of Panama, 1201 fathoms 
(‘‘ Albatross’’ station 3375). 
Distribution.—Gulf of Panama and vicinity; surface to 1832 fathoms (Faxon). 
Also taken off San Nicolas Island, California in 654 to 704 fathoms (‘‘ Albatross’’ 
station 4405). 
With respect to the great depth recorded for some of the captures of Hryonicus 
Faxon says (1895, p. 110): 
The huge spherical carapace of Eryonicus perhaps serves as a hydrostatic 
apparatus, by means of which the animal is enabled to lead a free-swimming life 
at some distance above the ocean bottom. The great depths of the soundings at 
some of the stations where Hryonicus has come up in the trawl may be delusive, 
as in the case of swimming Hoplophoridae and Sergestidae, which are often found 
in the trawl that has been lowered to great depths. At station 3388 [‘‘ Alba- 
tross,’’ Gulf of Panama], twenty-five miles from the nearest land, where the depth 
was 1168 fathoms, the Tanner self-closing net [described in Agassiz, 1892, pp. 
46-48] was lowered to 400 fathoms and towed for seventeen minutes. The net 
was hauled up to the surface after the lower part had been securely closed by the 
messenger at 400 fathoms. The lower part of the net was found to contain 
absolutely no life, while the upper part, which had remained open all the way 
from 400 fathoms to the surface, contained four specimens of Hryonicus, 19-29 
mm. long, together with other swimming forms [ Agassiz, 1892, pp. 48, 49]. At 
stations 3375 and 3383 [‘‘Albatross,’’? Gulf of Panama and vicinity], although 
captured in the trawl which had been lowered to depths of 1201 and 1832 fathoms, 
Eryonicus was found associated with several swimming forms. At station 3403 
[‘‘Albatross’’], a specimen of Lryonicus spinulosus [Faxon, 1895, p. 116] was 
brought up in the trawl where the bottom was only 384 fathoms. 
From these facts it is possible, if not probable, that Hryonicus leads a free- 
swimming existence at depths moderate compared with those frequented by truly 
