100 



CRUSTACEA MALACOSTRACA. 



as 85 mm. measured from the end of the antennal squama to the tip of the telson not a fortunately 

 chosen measurement. In the British Museum (Natural History) three antarctic specimens determined 

 by Sars are found; the specimen marked "type", a female with the marsupium scarcely fully developed, 

 measures 54 mm. from the front end of the rostrum to the tip of the telson; the largest of the two 

 other specimens, a female with the marsupium only half developed, measures 58 mm.; the third speci- 

 men is 49 mm. These southern specimens belong to a species very closely allied to, but not identical 

 with, B. scyphops, because there is a constant and very pronounced difference in the shape of the 

 eye-cups between the two forms. In the antarctic form, for which I propose the name B. distingucnda 

 n. sp., the eye-cup (fig. 2 a) is rather oblong, the proportion between height and length (the eye-stalk 

 omitted) being about as 17 : 25, and the protruding rim is broad, especially at the limit between the 



la 



la, 21 



Fig. I. Boreomysis scyphops G. O. Sars, 



i a. right eye, X 7 ; i b. right antennal 



squama, slightly more than X 6. 



Fig. 2. Boreomysis distinguenda n. sp. 



2 a. right eye, X 7; 2 b. right autennal 



squama, X 6 2 I$. 



upper and the posterior margin. In B. scyphops the eye-cup is relatively flatter and [higher (fig. i a) 

 the proportion between height and length being about as 21 : 26, the protruding rim is narrow, fre- 

 quently even narrower than shown in the figure, and the distal upper lobe at the front margin is 

 often rudimentary. A comparison between fig. i a and fig. 2 a will convey a good idea of the difference 

 in outline and excavation of the eye-cups in the two species. Finally the antennal squama is slightly 

 narrower in proportion to length in B. scyphops than in B. distinguenda. 



It may be added that I have a proportionately large material of Boreomysis from the Arctic 

 Seas, the Atlantic, the Indian Ocean and the Pacific; the material comprises nearly all hitherto 

 established and several undescribed species. Some species are closely allied, and a thorough study is 

 needed in order to avoid mistakes. 



6. Boreomysis tridens G. O. Sars. 



1870. Boreomysis tridens G. O. Sars, Christiania Vid. Selsk. Forhandl. for 1869, p. 153. 

 ! 1879. Monogr. Norges Mysider, III, p. 17, Tab. XIV. 



