SCH120PODA. 27 



therefore, fhe fourth and fifth pleopods will likewise be found to IMJ biarticulatc when 

 perfect specimens are examined. In H. antarctica only the fifth pleopods are 

 Inarticulate, the remaining pairs consisting of a single joint only. 



The eyes in the genus are described for the first time. They arc remarkable 

 chiefly for their small size and degenerate structure, for the complete absence of visual 

 elements, and the subservience, either entirely or in great part, of ophthalmic functions 

 to those of prolwbly a tactile nature. 



The cap-like form of the tergum of the first segment of the pleou recalls the 

 somewhat similar form of the third pleon segment in many Carida, and suggest* that 

 the posterior part of the body is capable of great ventral flexure. The ' Discovery ' 

 expedition is to be congratulated on the finding of this species, by far the most 

 interesting Schizopod in the collection. 



FAMILY MYSID^E. 







SUB-FAMILY LEPTOMYSIN.E, Norman. 

 GENUS PSEUDOMMA, G. 0. Bars. 



PsEUDOMMA BEUJNXB. 



(Plate VI., Figs. 1-8.) 

 Ptntdomma btlgifm, Holt and Tatteraall, 1906 (1). 



Locality of capture. Lat 78 25' 40" 8., long. 185 39' 6" E., 300 fathoms, one 

 specimen, immature female, 23 mm. 



Form (Fig. 1) compact and moderately stoutly built. 



Carapace (Fig. 1) large, less than half the total length of the body, covering 

 laterally all the segments of the thorax, but dorsally exposing the last one behind its 

 posterior emargination ; its anterior margin very slightly produced into a blunt, very 

 broadly rounded rostrum ; antero-lateral angles rounded ; cervical sulcus well marked. 



Pleon (Fig. 1), excluding the telson, about half the total length of the body from 

 the eye to the tip of the telson ; first four segments subequal in length and slightly 

 longer than the fifth ; sixth segment twice as long as the fifth. 



Eye plates (Fig. 1) contiguous, exhibiting only a very slight anterior median 

 cleft ; each plate subquadrangular or rhomboidal in shape, nearly twice as broad as 

 long, antero-lateral angles rounded, anterior margin nearly straight, no serrations or 

 armature of any kind ; no pigment present in preserved specimens ; corneal leans 

 absent, but the ramifications of the optic nerve arc clearly visible in dorsal view. 



Ant. a n til- 1 r peduncle (Fig. l) short and stout, not extending beyond half the 

 length of the antennal scale ; basal joint almost entirely covered by the ocular lamina-, 

 a few plumose seta; on each anterior corner ; second joint very short, more than twice 

 as broad as long, a few short setae on the outer distal corner, inner margin with a few 

 longer plumose setae ; third joint longer than either of the other two and slightly 



