98 U.S. NATIONAL MUSEUM BULLETIN 2 78 



Description. — Body smooth and quite slender, cephalon separated 

 from pereonite 1 by faint suture; however, not articulated. Length 

 of largest male 32 mm, largest female 23 mm. 



Articles in flagellum of antenna 1 variable in number, increasing 

 with increasing size of individual. Flagellum of antenna 2 biarticulate, 

 terminal article very small. 



Mandible with 3-segmented palp, setal formula for terminal article 

 varying from 1-5-1 to 1-27-1. Left mandible with 5-toothed incisor, 

 5-toothed lacinia mobilis, setal row of 3 serrate setae. Right mandible 

 with 5-toothed incisor, lacinia mobilis apically serrate, setal row of 

 2 serrate setae. Palp of maxUla 1 with 4-7 short apical spines and 3 

 or 4 setae on anterior surface; outer lobe with 7 apical spines, tending 

 to bifurcate with increased size of individual. Inner and outer lobes 

 of maxilla 2 variably setose. Outer lobe of maxilliped with 2 apical 

 setae, 1 long apical spine, and 3-7 small marginal spines; inner lobe 

 with 2 small spines, 6-12 apical setae of which 0-10 plumose; dactylus 

 of palp serrate at tip. 



Propodus of gnathopod 1 triangular with 2 proximal grasping spines, 

 grasping margins of dactylus and propodus serrate. Propodus of 

 gnathopod 2 with proximal poison tooth, grasping margin slightly 

 serrate proximally; dactylus not serrate. 



Pereopods 5-7, 6-segmented, propodus of male pereopod 5 with 

 pair of distal grasping spines, propodus of pereopods 6-7 of male and 

 female without grasping spines. 



Abdomen of both male and female with 2 pairs of biarticulate 

 appendages. 



Variation. — A comparison of a male and female (32 and 23 mm 

 respectively) from Tlior sta. 57 near Iceland with the small female 

 (7.5 mm) from off Cape Cod showed that no variation exists w^hich 

 cannot be accounted for by increased size of the animal. The setal 

 formula for the terminal article of the mandibular palp in the Cape 

 Cod female was 1-5-1 for the left mandible and 1-6-1 for the right 

 mandible. In the TJtor female the setal fornuda for both mandibles 

 was 1-27-1 and for the male it was 1-21-1. Six nonplumose setae 

 are present on the inner lobe of the maxilliped of the Cape Cod 

 female, 8 or 9 on the Thor male, of which 3 or 4 are plumose, and 12 

 on the Thor female with 10 plumose. 



Distribution. — Type-locality: Rognsund, off NE. corner of the 

 Island of Stjern0y (N. Norway, about 70°40' N.), at a depth of 

 200-350 m. 



Other records: Iceland, 63°21' N., 16°22' W., 500-560 m; Davis 

 Straits, 63°06' N., 56°00' W., 2258 m, and 61°50' N., 56°21' W., 

 2702 m. 



New record: Off Cape Cod, 42°00' N., 68^34' W., 174 m. 



