344 BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



median line. The fifth segment has eighteen spines, nine on either 

 side of the median line; they are arranged one on either side of the 

 median line, two in longitudinal series lateral to these, and two other 

 longitudinal series of three each, lateral to the others. The sixth seg- 

 ment has a transverse row of eight spines, four on either side of the 

 median line, with a smaller spine anterior to each one of the larger 

 spines with the exception of the two median ones. The seventh s<\o - 

 ment has eight spines in a transverse row, four on either side of the 

 median line, with a smaller spine on either side anterior to the most 

 lateral one. 



The abdomen is composed of two segments. The first segment has 

 two longitudinal rows of three spines in each row, one on either side 

 of the median line. Lateral to these are two spines on either side in 

 transverse series. The terminal segment has two longitudinal rows of 

 four spines in each row, one on either side of the median line; lateral 

 to each row is another small spine; the lateral margins of the segment 

 are produced on either side in two downward-projecting spines; it 

 terminates posteriorly in two long spines, one on either side of the 

 median line; at the base of the segment, between the longitudinal row 

 and the first laterally projecting spine is a smaller spine, one on either 

 side. 



The basis of all the legs is furnished with a small spine. 



PLEUROPRION INTERMEDIUM (Richardson). 



Arcturus intermedius RICHARDSON, Proc. U. S. Nat. Mus., XXI, 1899, pp. 854- 

 855; Ann. Mag. Nat. Hist., (7), IV, 1899, pp. 275-277; American Naturalist, 

 XXXIV, 1900, p. 230. 



Locality. Kyska Harbor, Aleutian Islands. 



Depth. 10 fathoms. 



Head with a deep excavation on its anterior margin, the antero- 

 lateral angles being produced in a double process, the inner one 

 rounded, the outer one acutely pointed. Near the anterior margin in 

 the median line is one large spine. Just back of the eyes and between 

 them are two long spines. The lateral margins of the head are pro- 

 duced in two small angulations with a rounded sinus between, poste- 

 rior to the double antero-lateral process. On the post-lateral margin 

 on either side of the head is a small spine. 



The first pair of antennae are small and short, not reaching to the 

 end of the second joint of the second pair of antennw. The first joint 

 of the second pair of antennae is visible and unarmed; the second joint 

 is armed with three spines; the third joint is unarmed, and is about 

 twice as long as the second joint; the fourth and fifth joints are 

 about equal in length and each is about twice as long as the third; 

 the flagellum consists of three joints. 



The first, second, and third thoracic segments have a transverse 

 row of six large spines, three on either side of the median longitu- 



