OECELLA. 415 



The present genus well illustrates tlie truth of these remarks, as it is at once 

 apparent that it has certain undoubted resemblances to Globicephalus, Grampus, 

 Orca and JPseudorca, whereas at the same time it so differs from each of them that 

 the only course left is to refer the two species to a distinct genus. The term Orcella, 

 however, is unfortunate, as in their external features they are not diminutive 

 representatives of the killers, as they have neither high fins to their backs nor very 

 broad pectorals. 



This Cetacean type was originally regarded by Owen ^ as a PJioccena, but it has 

 not the compressed teeth distinctive of that genus, from which it also widely differs 

 in the characters of its vertebral column and in its external features generally. 

 Dr. Gray^ at first considered it to be so nearly allied to Orca as only to merit sub- 

 generic rank to the killers. It is, however, as I have just mentioned, remarkably 

 distinct from these Cetaceans, as the dorsal fin, instead of being high and in the 

 middle of the back, is low and placed behind the middle of the body. Orca is also 

 distinguished by having extraordinarily large pectoral fins, nearly as broad as long, 

 whereas, in Orcella, the pectoral flipper, although proportionally much broader than 

 in Globicephalus, is only about half as broad as long. The pectoral limb, as a whole, 

 is also proportionally considerably longer and narrower than in Orca. Tliis is due 

 to the greater length of the bones of the arm and those of the metacarpus and 

 phalanges, which in Orca are relatively much less developed than in Orcella. In 

 the manus also other differences present themselves, as the second and third fingers 

 of Orcella are much longer than those of Orca, whereas the fourth and fifth are 

 rather shorter. Orca also is distinguished from Orcella by its much more power- 

 fully built skeleton with considerably fewer vertebrae, there being only a maximum 

 of 53 in it, to a maximum of 63 in Orcella. The cervical region of Orca, moreover, 

 has generally four or five vertebrae anchylosed, whilst in the two species of Orcella 

 the atlas and axis only amalgamate. Purther, in the Killers and Ca'ing whales 

 the ribs are transferred to the transverse processes at the 7th dorsal, whilst in 

 Orcella the transference does not take place until the 8th. In its conical teeth, 

 which are about the same number as in Orca, Orcella resembles the killers, and, 

 as pointed out by Eeinhardt,^ the breadth of the upper jaw in Orca is produced by 

 the maxillaries and not by the premaxillaries, as in Globicephalus, and in this 

 feature its skull resembles O^^ca. 



Dr. Gray, in his last work on the Cetacea,* separated Orcella from Orca, which 

 he elevated into a distinct family, the Orcadce ;^ elevating Orcella to generic rank 

 and placing it alongside Fseudorca, which he regarded as the type of a tribe of 

 Belphinidce. Fseudorca, however, has a much more depressed head than Orcella, 

 which is intermediate in this respect between Orca and Globicephalus. The dorsal 



1 I.e. 



2 Cat. Seals and Whales, 1866, p. 285. 

 M. c. p. 198. 



* Suppl. Cat. Seals and Whales, B. M. 1871, p. 80. 



* I. c. p. 85. 



