268 DEIPHINIDiE. 



This genus is easily known from Belphinus by the lowness of the 

 forehead, the short and depressed form of the beak, the posterior 

 position of the dorsal fin, the body being attenuated behind, and by 

 the breadth and flat, expanded form of the nose of the skuU. 



The OS hyoides of L. leueopleurus is laxge and broad. 



a. Seak elongate. Sostrum of shtM longer than the length of the brain- 



case. Teeth-Une some distance from the notch. Electra. 



b. Beak moderate. Rostrum of sktdl only as long as the brain-case. Teeth 



not quite to the notch. 



c. Beak very short. Bostrum of skull only as long as the brain-case. Teeth 



nearly to the notch. 



a, Rostrum of skull longer than the length of the brain-case. Teeth-line 

 some distance from the notch. Electra. 



1. Lagenorhynchus Electra. The Electra, 



Skull rather depressed; nose flattened above, expanded and re- 

 flexed on the side behind, rather shelving in front, sides rather 

 contracted in the middle, rather longer than the head, and once and 

 three-quarters the length of the width at the notch ; intermaxillary 

 broad, flattened, nearly two-thirds of the width, with a large, wide 

 groove for the greater part of its length ; triangle flat, rather con- 

 cave behind, with a lozenge-shaped, rather raised, rugose space in 

 the front half; teeth |^, rather small, cylindrical, conical, slightly 

 curved, acute, four in an inch ; the lower jaw regularly converging, 

 straight on the sides in front, rather swollen behind, and shortly 

 obliquely truncated in front, the gonyx rather produced. 



Lagenorhynchus Electra, Gray, Zool. Erebus Sf Terror, 35. 1. 13 (skull); 

 Cat. Cetac. B. M. 1850, 100. 



Inhab. ? 



a. Skull ? Purchased. The specimen figured in the ' Voyage 



of the Erebus and Terror.' 



SkuU: length, entire, 17| inches; of head, 8|; of nose, 9| ; of 

 teeth-line, 7 ; of lower jaw, 14| ; width of temple, 10| inches ; at 

 notch, 5| ; at middle of beak, 4 ; of intermaxillary, 2 J. 



This skuU is very Kke the former, but it is considerably larger, the 

 nose is longer in proportion, and the head is much more depressed 

 in the middle and spread out at the sides. 



2. Lagenorhynchus cseruleo-albus. 



Teeth -f-g- ; white, back bluish, with oblique streaks on the sides, 

 beUy white. 



Delphinus caaruleo-albus, Meyen, Act. Nat. Cur. xvi. 609. t. 43. f. 2 ; 



Gray, Zool. E. ^ T.4:2; Reichmb. Cetac. Anat. 1. 19 (skull). 

 Lagenorhynchus cseruleo-albus. Gray, Cat. Cetac. B. M. 1850, 100 ; 



Cassin, U. S. Expl. Exped. 81. t. 6. f. 2. 

 Delphinus albirostratus, Pecde, Zool. Expl. Exped. Mamm. 38, ed. 1, 1848. 



Inhab. East coast of South America, Eio de la Plata. 

 Length 5 feet 6 inches. Skeleton in Anat. Mus. Berlin. 



