428 PROCELLARIID2. 
HALOCYPTENA. 
Halocyptena, Coues, Proc. Acad. Philad. 1864, p. 78; Salvin, Cat. Birds Brit. Mus. xxv. p. 346 
(1896). ; 
The single member of this genus is a small brown bird, very similar to the Storm- 
Petrels in appearance, but differing in form. It may at once be distinguished by its 
cuneate or wedge-shaped tail. Like Procellaria, the present genus has the tarsus 
longer than the middle toe and claw, but it has also a very small bill, with prominent 
nasals which give the culmen a humped appearance. 
Only one species is known, which inhabits the seas and islands on the west coast 
of America from the Gulf of California to the Bay of Panama. 
1. Halocyptena microsoma. 
Halocyptena microsoma, Coues, Proc. Acad. Philad. 1864, pp. 79', 90°; Baird, Brewer, & Ridgway, 
Water-Birds N. Amer. ii. p. 402°; Towns. Proc. U. S. Nat. Mus. xiii. p. 141°; Salv. Cat. 
Birds Brit. Mus. xxv. p. 346°; Oates, Cat. Eggs Brit. Mus. i. p. 147, t. 11. fig. 1°. 
Fuliginoso-nigra, vix schistaceo adumbrata; tectricibus primariorum, ala spuria, remigibus et rectricibus 
nigerrimis ; tectricibus majoribus pallidioribus, brunnescentioribus, vix conspicuis; corpore toto subtus 
magis chocolatino-brunneo ; subalaribus pectore concoloribus, vix brunnescentioribus; tectricibus margina- 
libus nigris: rostro et pedibus nigris. Long. tota circa 5°5, ale 4°75, caude 2-0, culm. 0-4, tarsi 0-9, 
dig. med. cum ungue 0°7. (Descr. feminz adulte ex Mazatlan. Mus. nostr.) 
Hab. San Bentro Is. (Anthony®); Lower Catirornia, San José del Cabo (Xantus !? 3). 
—Mexico, Mazatlan (Morrer®); Bay or Panama (Townsend *). 
In general appearance this species resembles Procellaria tethys, but is distinguished 
by its wedge-shaped tail. It would appear to vary somewhat in size, as the female 
from Mazatlan has the wing only 4°75 inches in length (Salvin makes it but 4°65). 
A male from San Benito Island has the wing 4°55 inches, and a female from the same 
place 5:05. The Mazatlan bird is in somewhat worn condition, and does not show the 
browner greater upper and lower wing-coverts, as do the fresher plumaged birds from 
San Benito. 
H. microsoma was first discovered by the late John Xantus at San José del Cabo, in 
Lower California, and it has since been met with on some of the adjacent islands 
off the western coast. Mr. Forrer procured a single specimen near Mazatlan 5, 
and in March 1888 a bird of this species flew on board the ‘ Albatros’ in the Bay 
of Panama. 
Eggs collected by Mr. A. W. Anthony on the San Benito Islands are in our own 
collection and in that of the British Museum. They are of an elliptical or broad-oval 
shape, white, with a very few minute rufous dots—so small that they might easily 
escape notice—scattered all over the shell. 
