NATURAL SCIENCES OF PHILADELPHIA. 177 



side of a lower jaw retaining the symphysis ; from Chili Gulch, Calaveras Co., 

 and was submitted to Dr. L.'s inspection by Prof. J. D. Whitney, who is in 

 charge of the California State Survey. The specimen resembles, in its con- 

 dition of preservation, the Mauvaises Terres fossils of White River, Nebraska. 

 The formula of dentition is the same as in the Indian Rhinoceros, and the 

 proportionate size of the teeth was the same. It was about the size of R. oc- 

 cidentalism or perhaps a trifling degree larger, but its lateral incisors were triple 

 the size. The estimated length of the jaw is about 16 inches. The space 

 occupied by the molar series is 8 inches. Regarding the specimen as indicating 

 a species distinct from any of the preceding, the name of Rhinoceros hesperius 

 was proposed for it. 



September 2Qth. 



The President. Dr. Bridges, in the Chair. 



Thirty-two members present. 



On report of the respective Committees, the following papers were 

 ordered to be published : 



On a New Generic Type of SHARKS. 

 BY THEODORE GILL. 



In the year 1858 the Smithsonian Institution received, from Capt. Stone, 

 the jaws and vertebrae of an enormous species of shark existing in the Gulf 

 of California and known to the inhabitants of the neighboring regions as the 

 " Tiburon ballenas," or " whale shark." The specimen represented by the 

 spoils was said to have been "twenty feet long," with a " head six feet wide," 

 " pectorals three feet long " and " flukes six feet between tips.'' " The back 

 from the head to first dorsal fin, brown with reddish spots." The head is re- 

 presented as truncated in front. 



The dried dentigerous band of the upper jaw is slightly curved forwards, 

 about nineteen inches between the extremities, and somewhat more than an 

 inch in width in front. The teeth are fixed and extremely minute, the largest 

 being little more than a line in length, and decrease towards the ends of 

 the jaw ; they are disposed in regularly transverse rows, of which there are 

 over one hundred and sixty (164 167) on each side, while in front there are 

 from thirteen to sixteen in each transverse row ; each tooth is recurved back- 

 wards and acutely pointed, swollen and with a heel-like projection in front 

 rising from its base. 



This type will be seen, therefore, to be very distinct, but is evidently re- 

 lated to the South African genus Rhinodon, and must be referred to the family 

 of Rhinodontidee with the name of Micristodus punctatus. 



On two species of DELPHINIDiE, from California, in the Smithsonian 



Institution. 



BY THEODORE GILL. 



While examining the species of Cetaceans, represented by skulls and skins, 

 in the Smithsonian Institution, I discovered two species of Delphiuidse sup- 

 posed to have been hitherto undescribed. Brief descriptions of these are now 

 submitted ; at another time, it is proposed to give more extended descriptions 

 as well as figures. 



Lagenorhynchus obliqoidens, Gill. 



The skull in its generic characters agrees with that of L. leucopleurus, the 



1865.] 



