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552 ORNITHOLOGY AND OOLOGY. 
Famity PROCELLARIDZ. Tue PETRELS. 
Bill more or less lengthened, compressed, and deeply grooved, appearing to be 
formed of several distinct parts; the tip is strong, much hooked, and acute; the nos- 
trils open from distinct tubes, either single or double, and are situated at the base of 
the upper mandible. 
All the birds embraced in this family are strictly oceanic, some of the smaller 
species only being observed in bays near the ocean during or after a storm. They 
vary greatly in size, some being quite diminutive, while others are equal in dimen- 
sions to the largest known birds of flight. 
Two sub-families, namely, Diomedeine and Procellarine, constitute this family, 
the distinguishing characters of which are as follows :— 
DIOMEDEIN®. — Bill very strong, curved, and acute at the end; nostrils short, 
tubular, and situated on the sides of the upper mandible near the base. 
PROCELLARIN&Z. — Bill more or less strong, curved at the end, and pointed; 
nostrils tubular, situated on the culmen, near the base, and opening forwards. 
Sub-Family ProcerLtarine®. The True Petrels. 
The bill more or less strong, compressed, tip much hooked and pointed; the nos- 
trils tubular, to a greater or less extent, and situated on the basal part of the culmen; 
generally of medium or small size, wandering in their habits, and capable of sus- 
taining themselves on wing for a great length of time. 
THALASSIDROMA, Vicors. 
Thalassidroma, Vigors, Zool. Jour. (1825). 
Bill shorter than the head, slender and weak, the tip curved and acute, the sides 
compressed and moderately grooved; nostrils at the base of the culmen tubular 
and prominent; wings long and narrow, the second quill longest; tail forked or 
emarginate; legs slender and very long; tibia bare for a considerable space; ante- 
rior toes rather short and slender, united by an indented web; a short spur in place 
of the hind toe. 
THALASSIDROMA LEACHII. — Bonaparte. 
Leach’s Petrel. 
Procellaria Leachii, Temm. Man., II. (1820) 812. 
Thalassidroma Leachii, Nuttall. Man., I. (1884) 826. Aud. Orn. Biog., IIL. 
(1885) 484. Jb., Birds Am., VII. (1844) 219. 
