Boreomysis urospina

The body length of males is 33–36 mm, of females 35–40 mm. Color is uniformly red. Compared to other members of the genus Boreomysis B. urospina possesses a minute concavity on the lateral sides of the carapace anterior margin, and the proximal segment of the uropodal exopod is nearly half as long as the ramus. Compared to other species of the subgenus Petryashovia B. urospina has the widest uropodal exopod, which is about five times as long as wide, with three spiniform setae; and the endopod having three to five spiniform setae.

The most similar species within the subgenus is B. (P.) megalops. In addition to the unique features B. urospina differs from it also by the longer antennal scales, which are more than twice as long as the antennular peduncle and about five times as long as wide, unmodified pleopod 2 of male and the larger number of the telson terminal spiniform setae (four).

The telson length is 1.04–1.4 times the length of the abdominal segment 6, 2.9–3.5 times longer than wide, with its posterior width being 0.55–0.60 of the anterior width. Lateral sides are nearly straight, with 22–26 spiniform setae, which are nearly equal in length. The longest terminal spiniform setae are two to four times as long as the flanking ones. The cleft is 0.16–0.20 of the entire telson, without dilatation.

The eyes are extremely large, with the cornea dominating over the stalk, lacking papilla.^[2]

Boreomysis urospina is known only from the southern Tasman Sea south of Tasmania.^[2] The species takes an intermediate position between meso- and bathypelagic species. Found at the depth of 919-1086m, it is the most deep water member of the subgenus.^[2]