PROFESSOR FLOWER ON RISSO’S DOLPHIN. 19 
“Dents caduques; deux paires 4 la partie terminale de la miachoire inférieure 
seulement, D. griseus.” 
It now remains to be seen whether Fischer’s opinion is strengthened or the reverse 
by the new materials afforded by the two specimens described in the first part of this 
communication. 
As has just been shown, the differences hitherto noticed between the supposed species 
have resolved themselves into those of habitat, colour, and number of teeth. 
1. According to the previously observed habitats of the two species or varieties, the 
present specimens should be referred to D. griseus, as all the examples of D. rissoanus 
hitherto met with have been from the Mediterranean. 
2. According to the coloration, they should be D. rissoanus: but additional light is 
thrown upon this part of the subject by these two specimens; for they show conclusively 
how extremely variable the species is in this respect. This might be inferred from the 
absence of bilateral symmetry in the markings of each individual, shown most strongly 
in the adult example, where the markings were more profuse and complicated in cha- 
racter. Laurillard speaks of the ground-colour of the females being of a “ uniform 
brown,” and therefore quite different from that of the two specimens now described. 
Then, again, with reference to D. griseus, it must be remembered that the three descrip- 
tions all differ somewhat as to the colouring, and, especially, that in the figure of the 
type specimen from Brest numerous distinct irregular linear markings are indicated (as 
previously mentioned). These with the general “grisitre” colour would appear to 
show that it was more nearly allied in external characters to Risso’s Mediterranean 
Dolphin than to the black-and-white specimens described by D’Orbigny. If all the 
specimens of alleged D. griseus had been uniform in colour, and all those of D. rissoanus 
had presented another characteristic coloration, there would have been more grounds 
for keeping them distinct; but from the facts before us it is safer to conclude that we 
have here an example, very rare among Mammals, of a species of variable and irregular 
coloration. 
As to the teeth, the new specimens completely break down the specific distinction 
previously drawn; for, with the colouring of D. rissoanus, the adult one has the number 
of teeth assigned to D. griseus, viz. =< and that this is not the result of loss by age is 
satisfactorily proved by the young individual, in which the teeth had not even cut the gum. 
This last-named specimen was also extremely important, as presenting an undoubted 
case of original unequal number on the two sides, viz. three and four, showing that the 
exact number of teeth is a variable character ; and it also set at rest the question as to 
whether the absence of teeth in the upper jaw is a congenital peculiarity, or arises, as 
had generally been supposed, from their loss at an early age. 
It appears then necessary, until any better diagnostic characters are made out, to sink 
the specific name of rissoanus in that of griseus, though it may be convenient to apply 
the term “Risso’s Dolphin” to the peculiarly marked variety which was first made 
