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. 



Family MYSID.E. 

 PETALOPHTHALMUS W.-Suim. 



Zeitscbr, wissenscli. Zool., Vol. XXIV., p. xiv, 1874 ; Trans. Linn. Soc. London, 2d Scr., Zobl.,I. 43, 1875. 

 (lu part : so far as relates to the male.) 



In the above-cited papers Willemoes-Suhm described as male and female 

 of the same species PetalopMliahnus 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 leaf-like plate. The 

 male differed in a singular manner from the female in the form of the 

 carapace, antennce, mandibles, maxillipeds, gnathopods, telson, etc. In the 

 former the carapace was short, leaving the two posterior thoracic segments 

 exposed ; the second pair of antennae lacked the flagellum ; the mandibular 

 palps were enormously developed, forming a pair of very powerfid prehensile 

 limbs reaching far beyond the peduncle of the first pair of antennae ; 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 lamellse under the thorax, as in Boreom//sis 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 armiger " 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 1891,1 find one male specimen agreeing 

 in all the essential structural featiu-es with the male of rilalophthabnus armiger 

 Suhm, but differing in some trivial characters of merely specific value. Thia 

 specimen is figured on Plate LIV., under the name oi Pdalophthalmm paclfcus. 

 What is of more interest, I have discovered among the material dredged 

 during the cruise of the " IJlake " in 1877-78, a female Schizopod, 33 mm, 

 long (Station 29, lat. 24° 36' N., long. 84° 5' W., 955 fathoms) that closely 



* Rep. Cliallenger Scliizopoda, pp. 17i-177, Plate XXXIL Fig. 1-9. 



