202 UR WALTER M. TATTERSALL ON 



Museum, but the} 1 are mounted in Canada balsam, and are only to be seen in 

 lateral view. It was not possible to make sure either of the species of the host or 

 the form of the legs in the parasite. Until this matter can be settled, it is not 

 desirable to consider the differences noted above as specific. If the type host is 

 E. Kro/inii, the differences can only be regarded as varietal ; but, if E. americana, 

 the grounds for considering them specific are strengthened. On the principle 

 enunciated by GIARD and BONNIER, each species of host has a separate species of 

 parasite. The genus Heterophryxus would seem to be a favourable one in which 

 to test the truth of this axiom, for the form and shape of the last pair of legs 

 seem to afford more definite characters than are usually to be found in the species 

 of this group. It would be necessary to examine a large number of specimens taken 

 from definitely and accurately named hosts, to decide the point. In the meantime, 

 it seems to me to be best to refer the present specimens to the type species, with 

 a note on the differences they exhibit. 



Genus Dajus, Kroyer. 



Dajus siriellfB, G. 0. Sars. 

 D. sirieUx, G. O. Sars, 1885a. 



Scotia. 



Station 12, lat. 22 19' N., long. 22 07' W., tow-net. Several in the 



Cryptoniscan stage. 

 Station 14, lat. 21" 28' N., long. 22 40' W., tow-net. One female., with two 



males attached, from the incubatory pouch of Siriella Thompsonii. 

 Station 56, lat. 42' S., long. 31 20' W., tow-net. One female with male, 



free, but almost certainly from one of the thirty-eight specimens of 



Siriella Thompsonii in the same gathering. 

 Station 62, lat. 4 15' S., long. 3D 38' W., tow-net. Two females with 



males, from the incubatory pouch of Siriella Thompsonii. 



This species was originally described by SARS from specimens taken from Siriella 

 Thompsonii captured during the cruise of the Challenger. It has not, so far as I 

 am aware, been recorded since that time, until last year, when HANSEN (1912) noted 

 the presence of an Epicarid, probably this species, from the same host, captured in 

 the Eastern Pacific. 



The occurrence of two males with the same female is of interest. 



SARS' type specimens, both male and female, were immature, the male being only 

 in the Cryptoniscan stage. The present female specimens, presumably mature, have 

 the incubatory pouch prolonged backwards in two bluntly rounded projections, which 

 meet in the mid-ventral line and extend beyond the end of the pleon. The pouch is 

 also prolonged in front beyond the head, on either side. The segmentation of the 



(ROT. soc. EIJIN. TRANS., VOL. XLIX., 892.) 



