752 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
ENDOMYCHURA HYPOLEUCA (Xantus). 
XANTUS’S MURRELET. 
Adults in breeding plumage (sexes alike).—Upper parts, including 
whole of loral and upper half of auricular regions, slate color or deep 
slate-gray, the scapulars, interscapulas, and wing-coverts slate- 
blackish centrally, the primaries and primary coverts dull blackish 
slate narrowly margined with slate color; a narrow white crescentic 
mark beneath lower eyelid; entire under parts, except outer portion 
of sides and flanks, immaculate white; outer portion of sides and 
flanks slate-gray, some of the feathers tipped with white; under 
wing-coverts immaculate white; inner webs of primaries grayish 
white passing into gray distally and toward shafts; bill black, the 
basal portion of mandible pale bluish in life; iris dark brown; inner 
side of tarsi and upper surface of toes and webs pale blue (in life), 
the outer side of tarsi and under side of feet dusky. 
Winter plumage?—Similar to the summer plumage, but with white 
on sides of head involving most of the loral, suborbital, and 
auricular regions. 
Downy young.—Upper parts uniform black; under parts, including 
malar and suborbital regions, immaculate pure white; a flank-patch 
of grayish black or dusky gray, confluent with black of rump; thighs 
blackish. 
Adult male.—Wing, 118.1; exposed culmen, 19; tarsus, 24.1.2 
Adult female-—Wing, 113-127.5 (118.3); tail, 30-33 (81.3); 
exposed culmen, 15.2-23 (18); tarsus, 22-25 (23.8); middle toe, 
21.5-24.5 (22.7).° 
Coasts. and islands of southern California and Lower California, 
from Monterey Bay to Cape San Lucas;¢ breeding (at least formerly) 
on Santa Barbara and Los Coronados islands. 
Brachyrhamphus hypoleucus Xantus, Proc. Ac. Nat. Sci. Phila., xi, Nov., 1859, 
299 (Cape San Lucas, Lower California; coll. U. S. Nat. Mus.).—Batrp, 
Proc. Ac. Nat. Sci. Phila., xi, 1859, 306 (Cape San Lueas; crit.).—E.uiot, 
Illustr. New and Unfig. N. Am. Birds, pt. 8, 1867, (vol. ii), pl. 72.—CovEs, 
Proc. Ac. Nat. Sci. Phila., 1868, 64 (monogr.); Check List, 2d ed., 1882, 
no. 868.—Ripeway, Proc. U.S. Nat. Mus., iii, 1880, 211 (Cat. N. Am. Birds, 
no. 757); v, 1883, 534, footnote (Cape San Lucas and San Jose del Cabo); 
Nom. N. Am. Birds, 1881, no. 757.—Goss, Auk, i, 1884, 396 (at sea near 
San Diego, California, May 20, 1884; measurements, etc.). 
Blrachyrhamphus] hypoleucus Cougs, Key N. Am. Birds, 2d ed., 1884, 813. 
@ One specimen. 
b Six specimens. 
= Definite localities are: San Diego, Jan. 27; Monterey Bay (Sept. 2 to Apr. 25; 
July 29, several pairs); between San Pedro and Santa Catalina Island; near Santa 
Barbara; Santa Barbara Island; Santa Cruz Island; Los Coronados Islands (May 15, 
20), Guadalupe Island, San Benito Island, San Jose del Cabo, and Cape San Lucas. 
