NATURAL SCIENCES OF PHILADELPHIA. 47 



The young in the fall arc curiously variegated with dusky and 

 whitish above — few speciiuQns being exactly aJike. 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 croaking of some herons than the cries of the gulls 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 b}^ night, or at any rate in the dusk of evening, at 

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

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

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

 time, when the gulls and terns are 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 Ma}'. 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 evidentl}' been prevented from migrating by sickness, and 

 died shortl}' afterward. 



Podiceps cristatus. 



Occasional, in winter. (Specimen, January 29, 1810.) 



Fodilymbus podiceps. 

 Frequent, in winter. 



III. REPTILES. 

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

 Mass., for identification of some of the specimens. 



Sauria. 

 Cnemidophorus sexlineatus, D. & B. 



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

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

 1871.] 



