PUFFINUS. 433 
brunneis; subalaribus albis, margine alari brunneo: rostro saturate corneo; pedibus flavicantibus, 
digito externo saturatiore. Long. tota circa 17:0, ale 12-0, caude 5:6, culm. 1°45, tarsi 1°85, dig. med. 
cum ungue 2°15. 
9 a mari vix distinguendus. Long. tota circa 17-0, ale 11:5. (Descr. maris et feminze ex San Benedicto I. 
Mus. nostr.) 
Forma obscurior, Omnino fuliginoso-brunneus, corpore subtus vix cinerascentiore. (Descr. spec. ex San 
Benedicto I, Mus. nostr.) 
Hab. Lower Cauirornta, off Cape San Lucas (Anthony®); Revit.acicepo Is., San 
Benedicto I., Socorro I. (Anthony *® °).— Mexico, Maria Madre I. in the Tres Marias 
group (Nelson & Goldman").—Krusenstern I., N. Pacific!; WVoucano Is. 3; 
Hawallan Is. 9, 
This Shearwater was discovered on Krusenstern Island by Mr. H. J. Snow}, and 
was afterwards met with by Holst on Sulphur Island, in the Volcano group. Our 
principal acquaintance with the species rests upon the researches of Mr. A. W. Anthony, 
who found it in numbers on the Revillagigedo Islands and off the coast of Lower 
California °-®. Mr. Nelson also observed it near the Tres Marias’. | 
The species is dimorphic and has a white-breasted as well as a sooty phase. The 
latter has been described by Dr. Stejneger as P. knudseni, from the Hawaiian Islands 9 ; 
but Mr. Anthony found both forms on San Benedicto, and says that in a series of 
seventy-five examples every kind of intergradaticn was noticeable, from specimens with 
pure white underparts, including the under wing-coverts, to those in grey or sooty- 
brown plumage. These variations are plainly perceptible in the series in our collection, 
and it is noteworthy that Mr. Anthony records having taken examples of both phases 
out of the same hole. 
The same observer states that in the summer of 1897 he noticed this species about 
Socorro Island, but that it was not common there. None were seen at Clarion Island 
or west of Rocca Partida on this occasion, but subsequently he met with it at sea 
near the last-mentioned island. Both phases of plumage occurred, the sooty birds 
outnumbering the light-bellied ones by about two to one. It was not breeding to any 
extent at the time of his visit, and only a single egg was obtained. 
Mr. Nelson saw a considerable number of these Shearwaters at sea between Isabel 
Island and the Tres Marias, and he judged that they must be rather common in 
these waters. He noticed several among a flock of Sooty Terns which were following 
a school of porpoises ; but, as a rule, this Puffinus is found singly, skimming over the 
sea, making widely sweeping circuits, and pausing occasionally to pick up food’. 
Mr. Anthony has given a most interesting account of its habits, the bird having 
been found in abundance in May and June about Cape San Lucas, and between that 
point and the Revillagigedo Islands. The southern end of San Benedicto Island was 
honeycombed with their burrows. He considers that the nesting-season of P. cuneatus 
is at least two months later than that of either P. opisthomelas or P. auricularis, which 
both deposit their eggs during the early part of March. A rude attempt at a nest was 
BIOL. CENTR.-AMER., Aves, Vol. III., Apri] 1904. 55 
