NATURAL SCIENCES OF PHILADELPHIA. 293 



From these figures it appears the tree increased in growth only during the 

 three months between middle of May and middle of August, and that the 

 ratio of growth is much greater during the month between middle of June 

 and middle of Jul}' than during the month preceding and the succeeding 

 month. 



Third Coatribution to the History of the BAL.2SNIDJE and DELPHINID.E. 



BY EDWARD D. COPE. 



DELPHINIDJB. 



Orca destructor mihi sp. nov. 



Among the species of this carnivorous genus of Cetaceans, the present ex- 

 hibits the most compact and powerful stiucture, and it, no doubt, is fully 

 equal to any of them in its sanguinary habits. The breadth of the pre- 

 maxilliary bones allies it to the species c rassidens and rneridionalis, 

 which have ben called Pseudorca by some. 



It diffeis from the latter species in the greater breadth and obtuseness of 

 the muzzle of its cranium and mandible all we possess of it and in the 

 smaller number of teeth ; the premaxillary bones are relatively narrower 

 throughout the greater part of their length. 



The width of the muzzle at the lateral maxillary notch is a trifle less than 

 three-fourths the length from that point to the end of the muzzle ; the width 

 at the fifth tooth is a little greater, and quite'three-fourths that distance. The 

 prenarial triangle is smooth, concave on each side the medium fissure, and 

 extends to opposite the penultimate tooth. Teeth ?, the posterior tooth 



being the last of the maxillaries, instead of the mandibulars, as in rneridi- 

 onalis. The teeth occupy closely the intervals of the opposing series ; those 

 of the mandible are directed well outwards anteriorly. The intermaxillaries 

 form an elevated ridge exteriorly opposite the notch ; opposite the fifth tooth 

 above each is less than double the width of maxillary exposed exterior to it. 

 Behind the last tooth the margin of the maxillary is flared upwards in a 

 steep arch ; from opposite malar process to posterior tooth equals from pos- 

 terior margin of latter lo same of antepenultimate tooth. The mandibles are 

 much depressed distally, and the symphysis equals one-third the length of 

 the muzzle fiom the notch ; the chin projects beyond the broad extremity of 

 the premaxillaries. Measurements : 



in. lin. 



End of muzzle to glenoid cavity 20 7 



" " maxillary notch 11 6 



" " last tooth (straight) 9 6 



Length of symphysis 4 



" ramus mandibuli to condyle 20 3 



Breadth of muzzle at notch 8 45 



" " fifth tooth 8 6 



" " anterior tooth 4 



Depth of ramus at last tooth 3 1 



" " coronoid process 6 2 



One specimen (No. 3679) is in the Museum Smithsonian Institution, Wash- 

 ington, from the Southern Pacific ocean, off Paita, Peru. 



Beluga, angustata m. sp. nov. Beluga caiodon m. Proc. Academy, 1865, 278. 

 A study of the skeleton of the Beluga c a tod on (or leuca-i), deposited by thj 

 Smithsonian Institution in the Museum of Columbia College, Washington, 

 convinces me that the species which 1 formerly regarded as the same is really 

 quite different. For the present the following comparison will suffice : 



1866.] 



