282 ALLEN: NEW ENGLAND WHALEBONE WHALES. 



tBalaenoptera ?sursiplana COPE. 

 THE FOSSIL FINBACK OF GAY HEAD. 



PLATE 15. 



SYNONYMY. 



1842-3. Balacna Lyell, Proc. Geol. Soc. London, vol. 4, pt. 1, p. 33; Amer. Journ. Sci. and Arts, 1844, ser. 1, 



vol. 40, p. 320. 

 1895. Balaenoptera sursiplana Cope, Proc. Amer. Phil. Soc., vol. 34, p. 151. 



To this extinct species I shall provisionally refer certain bone fragments, chiefly verte- 

 brae, from the Miocene deposits of Gay Head, Martha's Vineyard, Mass., which are so 

 similar to bones of living Balaenoptera as to be practically indistinguishable. This species 

 was described by Cope from the Yorktown Miocene formation of Maryland on the basis of 

 the tympanic or ear bone, which indicates a whalebone whale of the size of the Common 

 Finback of the present day. Unfortunately it is impossible, on account of the dissociated con- 

 dition of the parts of the skeleton, to refer any vertebrae definitely to the whale that pro- 

 duced the ear bone, and no ear bones have been discovered in the Gay Head formation to 

 strengthen the supposition that the vertebrae there found are those of B. sursiplana. Yet 

 the species occurs in fossil condition throughout the Chesapeake Group of Maryland, and is 

 the only one referred to true Balaenoptera, so that its occurrence in these beds of correspond- 

 ing age is to be expected. 



Occurrence of the Fossils. 



The Miocene strata exposed at Gay Head are considered to correspond in age to the lower- 

 most or Calvert Formation of the Chesapeake Group. This is evidenced by the similarity 

 of the fossil mollusks in both beds. Further evidence for this I have recently found in the 

 discovery of a well preserved tooth of the extinct toothed whale, Basilosaurus [= Squalodon] 

 atlanticus from Gay Head, and now preserved in the Museum of Comparative Zoology. In 

 the Maryland Miocene this genus is as yet known from the Calvert beds only. 



At Gay Head the whale bones are found in a pebbly conglomerate underlying a stratum 

 of greensand (in which are numerous fossil crabs of a peculiar type). They are associated 

 with fossil sharks' teeth and casts of mollusks. Probably at least four genera of Cetacea are 

 represented among the various broken vertebrae in this hard conglomerate. The specimens 

 are chiefly centra with the neural spines or the lateral processes broken off, and present very 

 little that is especially characteristic. No doubt they are the remains of whales that were cast 



