NATURAL SCIENCES OF PHILADELPHIA 27 



Large in size, and very robust in form. Colors white and light pearl blue, 

 with darker primaries. 



As above defined, the genus Fulmarus is restricted to its type glacialis, 

 and tlie two other closely allied species pacificus and Itodgersii. 



As is the case with all the genera of the family, the name Procellaria has 

 been applied to the present genus. As I have already indicated,* I consider P. 

 pelagica and its congeners as typical of the genus Procellaria. Fulmarus appears 

 to be the first distinctive appellation of the present group ; having priority 

 over Rhantistes of Kaup. 



The type of this genus is subject to variations in size, etc., remarkable even 

 in this variable family. In consequence, several races or varieties have been 

 described aud named ; which I think are properly to be included under glaci- 

 alis. 1 recognize as valid the three following species. 



Fdlmarus glacialis (Linn.) Steph. 



Procellaria glacialis, Linn., S. N. 176(3, p. 213 ; et auct. nee Pall., nee Forst. 

 Fulmarus glacialis, Stephens, Gen. Zool. 1826, xiii. p. 234, pi. 27. Bona- 

 parte, Consp. Av. ii. 1856, p. 187 ; et al. auct. recent. 

 Fulmarus glacialis, var. Audubonii, Bonaparte, Consp. Av. 1856, ii. p. 187. 

 Fulmarus glacialis var. minor, Bonaparte, Consp. Av. 1856, ii. p. 187. 

 "Procellaria minor, Kjaerb," fide 13p. 

 "Procellaria h!/emalis, , ' Brehm. 



Habitat. North Atlantic Ocean. 



This species has served as the basis of so many nominal species, caused by 

 its great variations, that, although no description of it is needed, it may bo 

 well to notice the differences to be found whenever large series are compared. 



Examination of numerous specimens convinces me that the differences in 

 color are those of age and season chiefly if not wholly ; since the species passes 

 very gradually from the uniform dull greyish brown of youth to the pure white 

 and pearly blue of the adult condition. There do not seem to be any very 

 well defined stages during this transition. Birds of the year, before the autum- 

 nal moult, are entirely fuliginous gray, lighter beneath, with darker margins to 

 the feathers of the back and wing coverts. The tail is about concolor with 

 the rest of the plumage. There is an angular anteocular black spot. The bill 

 and feet are of a dull yellowish or ashy brown. After the moult, the pearly 

 blue of the back extends upon the nape and head ; (just as it does in Rissa 

 tridactyla ;) and the upper tail coverts, and the rectrices are of the same color. 

 The primaries are colored the same as in the mature bird. Spring and summer 

 adults have the pearl blue restricted to the back and wing coverts ; other parts 

 of the body being pure white. The distribution of colors is then just as in 

 Larus canus, argentatus, etc. The dark anteocular spot however seems perma- 

 nent. The bill is wholly yellow ; the feet yellow with a bluish tint. 



The variations in size are carefully to be noted ; since, taken in connection 

 with a varying length and robustness of bill, they have given rise to nominal 

 species. The average length appears to be about 16'5 inches; there is how- 

 ever a margin of one or even two inches both above and below this standard 

 to be allowed. The wing measures from the carpal joint to the tip of the 

 longest primary, from rather less than 11 to 12-5 inches. The average length 

 of the bill (chord of the culnien) is 1*5 ; but it may be l - 33 or 1-66, with a 

 corresponding difference in robustness. Young birds are always weak-billed. 

 The tail ranges from about 4 to about 5 inches. The average of the tarsus is 

 about 2 inches : of the middle toe without its claw, 2*25 ; both varying to 

 the extent of a fourth of an inch or rather more. The feet however as a general 

 rule differ less in dimensions than other parts. 



The synonomy of this species is very brief and uninvolved ; the points re- 



Proc. A. N. S. Philad'a. March, 1864, p. 79. 



1866.] 



I 



