34 
LORQUINIA 
scoters, or surf ckicks ( Oideuiia americana, O. deglandi and O. perspicil- 
lata), and the Harlequin Duck ( Histrionicus histrionicus) . The scoters 
obtain the shell fish principally by diving in shallow water and they will 
eat nearly any kind of small mollusc, which they swallow entire, the shell 
as well as the meat being- digested. The stomach of an adult male 
Surf vScoter ( O. perspicillata) examined at Forrester Island contained 
154 specimens of Margarita helicina and 893 specimens of Margarita 
laevior, besides other shells too far digested to be separated. 
The Harlequin Duck feeds mostly in the surf where it breaks 
against the rocks. This bird, like the oystercatcher, seems to prefer 
small limpets as its food and obtains them mostly without diving, 
picking them from the rocks, at or near the water's edge. The stom- 
ach of one Harlequin Duck examined by the writer contained 164 
small limpets, mostly Acmaea persona, but with a fair sprinkling* of 
the young of A. Patina and A. Pelta. 
The stomachs of a Dair of Pintail Ducks fDafila. acuta) taken at 
Sitka were full of littorines (Littorina sitchana). The Pintail, how- 
ever, is principally a vegetarian, probably eating few molluscs ex- 
cepting during its migrations up and down the coast. 
The common breeding gull of the locality (Lams glaiicescens) , 
though primarily a fish eater, often resorts to a diet of shell fish dur- 
ing a scarcity of its natural food. I have often observed these birds 
picking the soft parts from chitons and, in the vicinity of mud flats, 
they may be frequently seen extracting the meat from the shells of 
the large northern cockles (Cardinni corbis) that have been left ex- 
posed by the outgoing tide. 
A small pteropod (Limacina paciUca) is abundant at times during 
fine weather in some sections of southeastern Alaska. It swims 
through the water by means of two wing-like appendices and is eaten 
by gulls, grebes and other water birds, as well as by several species 
of fish. George: Willett. 
STUDIES IN ZOOLOGY II. 
Osteology— (The Skull) 
Preceeding the bony skull of vertebrates there is its counterpart in 
membranous form and in this the material is deposited which forms the 
permanent bony box. 
In all sharks and rays the skull does not advance beyond the carti- 
laginous stage though there is a greater or less deposition of lime salts 
giving the chondrocranium a varying degree of rigidity in the dififerent 
species and in the difterent individuals of different ages of the same 
species. 
