North Pacific Zoroasteride. 391 
adambulacral plates with a transverse series of five spines, 
the first deep in furrow, the second with a pedicellaria about 
1:5 mm. long attached to its base. 
Type-locality.—53° 12' N., 171° 37' W., 43°5 miles north- 
west of west point of Yunaska Island, Aleutian Islands, 
1217 fathoms, fine black sand; bottom temperature 35°2° 
Fahr. (U.S. Fisheries steamer ‘ Albatross,’ 1906). 
Zoroaster evermannt mordax, subsp. n. 
Closely resembling Z, evermanni*, but differing in having 
more robust primary spines (which are typically also a little 
shorter actinolaterally), and in having on the second from 
inner spine of prominent adambulacral- plates a large pedi- 
cellaria (or sometimes two), from 1°5 to 2°5 mm. long, and 
conspicuously bigger than the cluster of small pedicellariz on 
the furrow-spine. R=153 mm., r=10+ mm., R=15r. 
Type-locality.—Off Washington, 47° 28’ N., 125° 15’ W., 
477 fathoms, green mud. 
This race is distributed from off Washington to southern 
California. At the southern end of its range it is found 
only in water deeper than 600 fathoms, while the typical 
evermannt occurs from San Diego, California, to Santa Cruz 
Island, California, in 216 to 510 fathoms. 
Key to the North Pacific Species and Subspecies of 
Myxoderma. 
a’. Size large (R, 200 mm.). The plates and 
spines invested in a thick pulpy membrane, 
slimy inlife; abactinal papular areas large, 
the dorsal skeleton being open and rather 
irregularly reticulate at base of ray; 
abactinal plates without accessory spinelets 
to any extent; actinolateral spines pointed, 
tapered, sometimes somewhat flattened, 
but never spatulate ; terminal plate large, 
ovoid, especially conspicuous in young 
specimens ; rays attenuate distally. 
b'. Rays thicker and skeleton stouter, third 
or lowest series of actinolateral plates 
extending five-eighths the length of ray ; 
abactinal spines robust and stubby; 
‘ 
* Zoroaster evermannt, Fisher, Bull. Bureau Fisheries, 1904, vol. xxiv., 
June 10, 1905, p. 317. Further investigation has shown that this is not 
a Myzoderma, as it lacks the essential anatomical characters of that 
genus. : 
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