44 BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



small furrow spine and a larger actinal spine, with sometimes a third smaller spinule 

 external to the latter. 



Type— Cat. No. 37040, U.S.N.M. 



Type-locality.— Station 3073, off Washington, 47° 28' N., 125° 15' W.; 477 

 fathoms, green mud; bottom temperature, 49.2° (?) 5 specimens. 



Distribution. — From off Washington to southern California, 239 to 760 fathoms; 

 in south only in over 600 fathoms. 



Specimens examined.— Station 3069, off Washington, 47° 25' 30" N., 125° 42' 

 W.; green mud, 760 fathoms; bottom temperature, 37.6° F.; one specimen. 



Station 3349, off northern California 38° 57' 45" N., 124° 03' 05" W.; 239 

 fathoms, black sand; bottom temperature, 44.1° F.; one specimen. 



Station 2980, off southern California, 33° 49' 45" N., 119° 24' 30" W.; 603 fath- 

 oms, green mud; bottom temperature, 38.9° F.; 33 specimens. 



No locality, 11 specimens (label lost during earthquake, 1906). 



Remarks. — Although the differences which separate this race are not great, they 

 are constant as regards the pedicellariae; the spines fluctuate a little and the dis- 

 tinction is not very evident except on direct comparison. In the southern California 

 examples the spines are scarcely heavier than in the typical form from shallower 

 water, but the pedicellariae are very well developed. 



It is interesting that this race, or at least the differences which characterize the 

 race, are found in specimens from 603 fathoms off Anacapa Island, southern Cali- 

 fornia, bottom temperature 38.9°. It is probable that the high bottom temperature 

 of 49.2° recorded for station 3073 is a misprint or a mistake; it is more likely between 

 38° and 39°, judging from records of neighboring stations. 



Genus MYXODERMA Fisher 



Myxoderma Fisher, subgenus, Bull. Bur. Fisheries, 1904, vol. 24, June 10, 1905, p. 316. 

 Type, Zoroaster (Myxoderma) sacculatus Fisher; Ann. and Mag. Nat. Hist., ser. 9, vol. 3, 

 1919, pp. 389, 391 (genus).— Clark, Mem. Mus. Comp. Zool., vol. 39, no. 3, 1920, p. 99. 



Diagnosis. — Zoroasteridae resembling Zoroaster more closely than any other genus, 

 yet differing in having a more open abactinal skeleton with relatively smaller carinal 

 plates and smaller, usually trilobate, irregularly oriented adradial plates bounding 

 good-sized papular areas often irregular in contour; differing absolutely in the pos- 

 session of well-developed superambulacral ossicles, and especially in the development 

 of the first superambulacral ossicle into a heavy buttress or bridge, uniting the enlarged 

 upper end of the first ambulacral ossicle with the body wall at the interradius; 

 gonads two to each ray and attached to side of the ray close to interbrachial angle; 

 ampullae single, with a very rudimentary second lobe; ambulacral furrow wide proxi- 

 mally; tube-feet four-ranked ; three actinolateral series of plates below inferomarginals. 



Remarks. — Originally I included Zoroaster evermanni in the subgenus Myxoderma. 

 A further study of more extensive material, as well as the subsequent description of 

 a new species, Zoroaster platyacanthus H. L. Clark, has provided additional means of 

 testing the naturalness of this group. I have greatly emended the original descrip- 

 tion by the addition of the features which sharply demark Myxoderma from Zoroaster, 

 namely, the possession of superambulacral plates, and the specialization of the first 

 superambulacral ossicle into a sort of flying buttress between the enlarged upper end 



