PETALOPHTHALMUS. 221 
The specimen from Station 2619 (Plate K, Fig. 2) is apparently a young 
female. It was caught in the Tanner net which had been towed at a depth 
of 1000 fathoms (100 to 400 fathoms above the bottom), and drawn up 
closed. 
Famity MYSID Ai. 
PETALOPHTHALMUS W.-Sunm. 
Zeitschr. wissensch. Zool., Vol. XXIV., p. xiv, 1874; Trans. Limn. Soc. London, 2d Ser., Zool., I. 43, 1875. 
(In part: so far as relates to the male.) 
In the above-cited papers Willemoes-Suhm described as male and female 
of the same species Petalophthalmus armiger, two interesting Atlantic Schizo- 
pods from the “ Challenger” Expedition characterized by the atrophy of 
the eye and the conversion of the eye-stalk into a leaflike plate. ‘lhe 
male differed in a singular manner from the female in the form of the 
carapace, antenne, mandibles, maxillipeds, gnathopods, telson, etc. In the 
former the carapace was short, leaving the two posterior thoracic segments 
exposed; the second pair of antenne lacked the flagellum ; the mandibular 
palps were enormously developed, forming a pair of very powerful prehensile 
limbs reaching far beyond the peduncle of the first pair of antenne; the 
maxillipeds and the gnathopods were devoid of exopods; the telson was 
truncate and entire at the distal end. In the female, on the other hand, the 
carapace covered the posterior part of the thorax, the telson was deeply 
incised, and the appendages presented the normal form. There were seven 
pairs of incubatory lamella under the thorax, as in Boreomysis G. O. Sars, 
to which genus the specimen conformed in most regards. When the “ Chal- 
lenger” Schizopods were afterwards placed in Professor Sars’s hands, the 
female of “ Petalophthalmus arniger”’ had been lost, so that no further account 
of the specimen was published. The male was redescribed and figured by 
Sars with great care.* 
In the “ Albatross” collection of 1891, I find one male specimen agreeing 
in all the essential structural features with the male of Pefalophthalmus armiger 
Suhm, but differing in some trivial characters of merely specific value. This 
specimen is figured on Plate LIV., under the name of Petalophthalmus pacificus. 
What is of more interest, I have discovered among the material dredged 
during the cruise of the “ Blake” in 1877-78, a female Schizopod, 33 mm. 
long (Station 29, lat. 24° 36’ N., long. 84° 5’ W., 955 fathoms) that closely 
* Rep. Challenger Schizopoda, pp. 174-177, Plate XXXII. Fig. 1-9. 
