NATURAL SCIENCES OF PHILADELPHIA. 15 



Anterior ribs single headed ...Balrenoptera. 



Anterior ribs double headed Sibbaldius. 



Those engaged in the pursuit of whales recognize these natural groups with- 

 out difficulty, as evidenced by their vernacular names of long standing. Thus 

 the species of div. I are " right whales," of II A, " scrag whales ;" of II B a, 

 " humpback whales ;" and the Balajuopteras, etc., " finner whales." The last 

 are most numerously represented by species. 



BAL^^NA Linn. 



Two species of this genus have been described by authors as inhabiting 

 the North Pacific Ocean, though the materials upon which their identification 

 has been based is of the most slender description. I am as yet unable to de- 

 termine to which of them the right whale mentioned by Capt. Scaramon should 

 be referred. I therefore enumerate both here. A third species, the Bow Head 

 of American whalers, is stated to pass south of Behring's Straits at certain 

 seasons of the year, according to Capt. Scammon. I enumerate it as the same 

 as the Greenland Right Whale of English authors, which is the " bow-head " 

 of the Eastern American whalers, in contradistinction to the Right whale, (B. 

 c i s a r c ti c a), 



Bal.'Kna mysticktus Linn. 



Bow-head. Catal, Whales and Seals, Brit. Mus. p. 81. 



Bal/Ena sieboldii Gray. 



Cat. B. M. 96, Balenna auslralis Temm. Faun. Japon. t. 28, 29, (from Japanese 

 model). 



BaLvENA cdllamach Chamisso. 



Nova Acta, Acad. Curs, xii, 251 Tab. (from Aleutian model). Cope, Pr. A. N. 

 Sci. Phil. 1868, 225. 



RHACHIANECTES Cope. 



This genus is now first characterized. Its only known species I originally 

 united with Agaphelus Cope, but the form of the scapula is so different that 

 it must be distinguished. While that of Agaphelus is identical with that of 

 Balaeuoptera, it is in the present genus quite like that of Baliicna. 



Rhachianectes glaucus Cope. 



Agaphelus glaucus Cope, Proceed. Academy Nat. Sciences, Philada. 1868, p. 



225. The California Gray Whale. 



This species was originally described from specimens by Wm. H. Dall, of 

 San Francisco. 



MEGAPTERA Gray. 



In this genus the rudiment of a dorsal fin exists as a hump on the posterior 

 part of the dorsal region. The fins are longer than in any other genus, and 

 two or more of the cervical vertebriE are occasionally more or less coossified. 

 The following species are known more or less imperfectly : M. longimaaa 

 Rudolphi, from the Arctic Seas ; M. o s p h y i a Cope, from the Western At- 

 lantic ; M. brasiliensis Gray, [Balxnoptera Gray), from the coast of Bra- 

 ail ; M. 1 a 1 a n d i i Fischer, from the Cape of Good Hope : M. k u z i r a Gray, 

 from the Western Pacific. The full measurements and description of Capt. 

 Scammon enable me to add another species, viz.: 



Megapteua veksabilis Cope. 



Spec. nov. The North Pacific hump-back. 



This species possesses pectoral fins, apparently intermediate in length be- 

 tween those of ihe M. longimaaa and the species with shorter fins, as M. 



1869.] 



