54 Dr. J. E. Gray on Emys nigra yrom Upper California. 



These measurements prove that the cranial part of the skull 

 is relatively somewhat larger in Ps. Grayi than in Ps. crassi- 

 dens, and that the whole animal may have been consequently 

 stronger and stouter than the European species, exceeding the 

 Australian one still more in both qualities. 



The description and figures of the swimming Delphinide, 

 seen by myself in the Atlantic Ocean and published in my 

 * Anales/ p. 368, do not belong to the Pseudorca Grayi, as I 

 supposed, but to a true Glohiocephalusy which cannot be deter- 

 mined exactly without further observations. 



Buenos Ayres, April 24, 1872. 



VI. — On Emys nigra from Upper California. 

 By Dr. J. E. Gray, F.E.S. &c. 



Emys nigra of Hallo well is said to be the same as Emys 

 marmorata of Baird and Girard, which Agassiz, in his great 

 work on the Natural History of the United States (of which 

 only the general observations and the tortoises have appeared), 

 refers to the genus Actinemys, and figures the young of the 

 species ; and on his authority (for I have never been able to 

 see the species) I have arranged it under Geoclemmys (see 

 Cat. Shield Reptiles, Suppl. p. 27). 



In Hallowell's Report on the Reptiles collected in the 

 Survey for the Railroad from the Mississippi to the Pacific 

 Ocean, 1859 (a work which I had not previously consulted), 

 he describes and figures Emys nigra, which he says is very 

 abundant in Posa Creek, northern part of Upper California. 

 The figure represents a very depressed watev-Emys, with a 

 dark narrow band across the eye, broad webbed feet, with 

 acute elongated claws. The head appears to be covered with 

 a uniform skin, not divided into symmetrical plates. The 

 limbs and tail are marked with large black spots ; and the 

 upper part of the head and neck is blackish, with numerous 

 small yellow spots. 



The skin of tlie head and limbs more resembles that of the 

 true Terrapins than any other American species I know ; and 

 it would be very interesting to know the form of the jaws. It 

 certainly is a purely aquatic tortoise, and has nothing to do 

 with the more terrestrial tortoises of America forming the 

 genus Geoclemmys or Actinemys. 



Mr. Hallowell's figure is very like a specimen that I ob- 

 tained at Nantes, and which I described and figured as Emys 

 olivacea'm the 'Catalogue of Shield Reptiles,' p. 30, t. 12 c,. 

 and which is named Redamia olivacea in the Supplement to 

 that Catalogue, p. 35. 



