Pacific Coast of North America. 275 



Fourth segment of thorax not greatly longer than others. 

 Marsupium of female composed of four pau's of plates. Pos- 

 terior thoracic legs biunguiculate. 



Analytical Key to the Species 0/ Arcturus ■'^. 



a. End of abdomen notched as seen from 

 above. 

 b. Rod}^ smooth and free from spuiea . . 61. A. heringanus, Benedict. 

 b'. Body spiny. 



c. Head and six segments of thorax 

 each with a pair of spines on the 

 dorsum. Second and third articles 



of antennas without spines 61'. A. kinjispinis, Benedict. 



c'= Head and segments of thora.x with 



not less than two pairs of spines 



to the segment. 



d. Head wifh one large median spine 



on anterior part of head in front 



of eyes 63. A. intermedius, sp. n. 



d'. Head with three spines on ante- 

 rior part of head in front of eyes. 64. A. Murdochi, Benedict. 

 a'. End of abdomen without notch 65. A. glaber, Benedict. 



61. Arcturus heringanus^ Benedict. 



Ardunis heringanus, Benedict, Proc. Biol. Soc. Washington, xii. 18!}8, 

 pp. 46, 47. 



Hah. Alaska ; Bering Sea, 



62. Arcturus longispinis, Benedict. 



Arcturus hngispinis, Benedict, Proc. Biol. Soc. Washington, xii. 1898, 

 pp. 44, 45. 



Hah. Aleutian Islands. 



63. Arcturus intermedius^ sp. n. 



Head with a deep excavation on its anterior margin, tho 

 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 produced in two small angu- 

 lations, with a rounded sinus between, posterior 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 



* Dr. Benedict's key is used in part for the genus Arcturus. Proc. 

 Biol. Soc. Washington, xii. (1898) pp. 42, 43. 



