NATURAL SCIEXCES OF PHILADELPHIA. 4Y 



The young in the fall are curiously variegated with dusky and 

 whitish above — few specimens being exactly alike. The note of 

 this species is instantly distinguished from that of any of our other 

 species of this family b}^ its deep guttural intonation, more like 

 the croakino; of some herons than the cries of the o-ulls and terns. 

 The bird also differs from its allies in going in true flocks, as 

 distinguished from the gatherings, however large, in community 

 of interest, that occur with the gulls and terns. The birds move 

 synchronously, which is not the case with any of the others. They 

 feed chiefly by night, or at any rate in the dusk of evening, at 

 which time, in passing over the harbor, one maj^ hear their hoarse 

 notes on every hand, and see the birds gliding swiftly along just 

 over the water, either singly or in small flocks. During the day- 

 time, when the gulls and terns ai-e busy fishing, the skimmers are 

 generally seen reposing on the sand-bars, and they never drop on 

 their prey like their allies. Their mode of feeding is not exactly 

 made out, but it is believed they skim over the surface with the 

 body inclined downward, the bill open, and the under mandible in 

 the water, so that they really take their prey in a manner analo- 

 gous to the feeding of whales. 



Colymbus torquatus. 



Abundant winter resident, from the latter part of September 

 until Mixy. The greater part, however, do not arrive until some 

 time in October, and a few linger through a portion of Ma^'. I 

 took one full-plumaged bird alive in the latter part of June ; but 

 it had evidently been prevented from migrating by sickness, and 

 died shortly afterward. 



Podiceps cristatus. 



Occasional, in winter. (Specimen, January 29, 1870.) 



Podilymbus podiceps. 

 Frequent, in winter. 



III. KEPTILES. 

 I am indebted to my friend Mr. J. A. Allen, of Cambridge, 

 Mass., for identification of some of the specimens. 



Saitria. 



Cnemidophorus sexlineatus, D, & B. 



Yery abundant on the islands and sandy parts of the adjoin- 

 ing mainland. They appear usually early in April, and may be 

 1871.] 



