484 DR. H. BURMEISTEU ON PONTOPORIA BLAINVILLII. [May I), 



4. Preliminary Observations on the Anatomy of Pontoporia 

 blainvillii. By Dr. H. Burmeister, F.M.Z.S. 



Some weeks ago one of my friends brought me the dry body of 

 a specimen of Pontoporia blainvillii, which was taken hving in the 

 mouth of the River Gueguen Grande, in 38° 33' S. lat. The body 

 had lost all the external flesh and the greater part of the viscera, 

 and could only be made use of for a skeleton, which is now exhi- 

 bited in the public museum of Buenos Ayres. 



As the internal structure of this interesting animal is entirely 

 unknown, I beg leave to communicate to the Zoological Society my 

 observations made during the examination of the body, some of them 

 being very curious, and worthy, as I believe, to be known to science. 



I will not speak of the general figure of the animal and its colour, 

 because most of the external surface was lost ; but I may mention 

 that another entirely well preserved individual in our museum has no 

 trace of the white stripe on each side of the body which is repre- 

 sented in D'Orbigny's figure (Voyage, Mamm. pi. 23). The upper 

 part of the whole body is blackish grey, and the whole underside white, 

 which colour extends halfway up the sides, and occupies also the 

 under jaw and the sides of the head. But the general figure of both 

 animals is the same, and therefore I cannot doubt that my species 

 is the same as that figured by D'Orbigny. 



As the skull is already well known by the figure in the work above 

 mentioned, I will not enter into a description of that part of the 

 skeleton, especially since Mr. Flower, one of the best-informed ob- 

 servers of the skeletons of the Cetacea, is occupied with a compa- 

 rative description of the skulls of Pontoporia and Inia, the former 

 sent by myself to Dr. J. E. Gray for the British Museum. 



I will therefore begin my description with the vertebral column, 

 which is composed of forty-two vertebrae, divided into seven vertebrae 

 of the neck, ten of the back, seven of the lumbar portion, and 

 eighteen of the tail, of which the first five are provided with infe- 

 rior spines or hsemapophyses. 



The seven vertebrae of the neck are all free, and none of them 

 anchylosed; they have together an extent of 1" 10'", each of the 

 first two being 5'" long, and the five others 2^'". Only the second 

 vertebra has a strong reclined spinous process, and very broad thick 

 transverse processes ; the five following have no spinous processes, 

 but transverse processes of different size and form. The transverse 

 process of the third vertebra is somewhat larger than the same part 

 of the fourth, and the fifth vertebra has the smallest transverse pro- 

 cess of all ; but on the lower margin of the body of the same ver- 

 tebra springs up another thick and short tubercle, which is already 

 indicated on the fourth vertebra, and presents itself also on the two 

 following. To this lower tubercle of the seventh cervical vertebra 

 is attached the capitulum of the first rib. 



The ten dorsal vertebrae have together an extent of 6 inches, each 

 one being somewhat longer than its predecessor ; so that the first is 



