300 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



Diagnostic features. This species appears to differ from asperrima, only in having 

 the third syzygy usually between brachials 16 + 17, sometimes between brachials 15 + 16, 

 and in having generally a greater development of spines on the edges and dorsal sur- 

 faces of the ossicles of the division series and proximal brachials. 



It appears to differ from tanneri in having the distal edge of the proximal segments 

 of the oral pinnules produced into a more or less carinate process, which makes the 

 pinnule bases appear much stouter; and from mariae in having shorter brachials, the 

 longest of these being broader than long. 



In the southern part of its range Fariometra parvula is found associated with this 

 species, to the young of which it bears a close superficial resemblance. In Fariometra 

 parvula, however, the centrodorsal is sharply conical, the third syzygy is between 

 brachials 14 + 15, and the distal intersyzygial interval is 2 muscular articulations. 



Notes. As the detailed description of asperrima (excepting for the position of the 

 third syzygy, which in serratissima occurs usually between brachials 16 + 17) applies 

 almost equally well to this species, there seems to be no necessity for repeating it. 



The development of spines on the edges, and often also on the dorsal surface of the 

 ossicles of the division series and the proximal brachials, reaches a much greater ex- 

 treme in serratissima than in asperrima, and the average spinosity is also greater. But 

 in both species individuals occur in which the arm bases are almost smooth. 



The maximum arm length in this species is slightly less than that of asperrima, 

 though the average is about the same. The arm length in fully developed individuals 

 is usually between 150 and 200 mm. 



The maximum development of spines occurs in specimens from Albatross sta. 

 3461, in Puget Sound. In these the borders of the ossicles of the division series and 

 lower brachials are frilled with irregular long spines, and the dorsal surface of the 

 division series and first two brachials usually bears scattered spines which may become 

 so numerous as completely to cover them. Sometimes these spines are simple, and 

 sometimes they are branched or tufted, rising from a conical base. Occasionally the 

 second brachial and the axillary may show a more or less regular row of conical tufted 

 spines in the median line. Other extremely spiny specimens are from stas. 2877 and 

 2459, at the entrance to Puget Sound, from sta. 3109, off San Mateo County, California, 

 and from sta. 2959, off southern California. The depth at these stations ranges from 

 73 to 225 meters, and the temperature from 6.89 C. to 11.05 C. 



Specimens varying from very spiny to only slightly spiny, or even almost entirely 

 without spines, are at hand from stas. 2893, 2956, 4555, 4543, 4518, 3129, 3672, 3078, 

 3789, 3449, 3454 and 3452, representing localities from Puget Sound to the Santa 

 Barbara Islands in from 95 to 265 meters, with temperatures from 6.78 C. to 9.44 C. 



Moderately spiny individuals only were dredged at stas. 4384, 4375, 2952, 2954, 

 2955, 4554, 4535, 4553, 4460, 3350, 3446, 3464 and 4245, representing localities from 

 southeastern Alaska to San Diego, California, in from 73 to 254 meters, with tempera- 

 tures ranging from 6.95 C. to 9.39 C. 



Moderately to only slightly spiny specimens were dredged at stas. 3119, 4552, 

 4471, 4463, 4461, 3108, 3163, 3051 and 3445, and were sent me by Prof. McLean Fraser 

 from Nanaimo. These localities range from Puget Sound to Santa Cruz, California, 

 the depths being from 79 to 652 meters and the temperatures from 6.67 C. to 10.50 C. 



