368 BULLETIN OF THE 



179. Sterna macrura Neumann, Arctic Tern. 

 "Common at Dummitt's." — Maynard. 



As already remarked under Sterna hirundo the individual variation in 

 the present species is very great. The largest and smallest specimens in 

 a series of twenty-five, taken at Muskeget Island in the breeding season 

 measured as follows : — 



Largest {$) : Length, 16.00; alar extent, 32.75; wing, 11.75; tail, 6.00. 



Smallest (<?) : Length, 14.33 ; alar extent, 27.52 ; wing, 9.85 ; tail, 4.26. 



The maxima and minima of this series are as follows : — 



Length, 14.10 and 17.00; alar extent, 27.52 and 32.75; wing, 9.85 and 

 11.84; tail, 4.26 and 8.25. 



"While the females average a very little smaller than the males, several 

 of the females are very nearly as large as the largest males. 



The Sterna Forsteri may also occur as a winter resident, but I have 

 at present no evidence of its occurrence there at this season. A specimen 

 from the " St. John's River, Florida," collected by Dr. "Wurdemann, is 

 ■cited by Mr. Lawrence * and Dr. Coues f (Smithsonian collection No. 

 4928), but no information is given as to when it was collected. 



180.* Rhynchops nigra Linn€. Black Skimmer. 

 Abundant on the coast, occurring in large flocks. Not observed by 

 me on the St. John's. 



COLYMBIDJE. 



181 .t Colymbus torquatus Brunnich. Loon. 



" A single specimen at Mandarin, on the Lower St. John's ; abun- 

 dant off Fernandina harbor." — Maynard. 



The considerable number of specimens of this species in the Museum of 

 Comparative Zoology show a wide range of individual variation. In a 

 series of fifteen specimens from various localities in New England, but 

 mainly from Massachusetts, the variation in the length of the folded 

 wing amounts to twenty per cent of its average length in the whole se- 

 ries ; in the length of the tarsus, to twenty-nine per cent ; in the length of 

 the outer toe, to thirty per cent ; in the length of the head, to twenty- 

 eight per cent ; and in the length of the culmen to twenty-three per cent. 



The form described some years since as Colymbus Adamsi seems to have 

 been founded on very old specimens of the large northern race of C. tor- 



* Baird's Birds of North America, p. 863. 

 t Proc. Acad. Xat. Sci. Phila., 1862, p. 547. 



