PROF. W. H. FLOWER ON THE GENUS MESOPLODON. 425 



breadth of l"-3 = 34 millims ; in M. grayi, a length of 5"*3 = 135 millims. and a 

 breadth of l"-0 = 26 millims. 



Dental characters. — All the Ziphioid Whales have previously been characterized as 

 baving " no functional teeth in the upper jaw. Teeth of mandible quite rudimentary 

 and concealed in the gum, with the exception of one or occasionally two pairs, which 

 may be largely developed, and project like tusks from the mouth, especially in the 

 male sex" 1 . 



A series of small rudimentary and concealed teeth has been shown to exist in the lower 

 jaw, behind the large functional teeth, in Mesoplodon bidens, by Gervais, in the upper 

 jaw oiZipkius cavirostrisby Gervais, and in both the upper and lower jaw of a member 

 of the same genus, if not species, by Burmeister ; and they may have been present, but 

 overlooked, in many other specimens, as such teeth, not being fixed in the bony 

 alveoli but only attached loosely in the gums, would invariably be lost by maceration. 

 The discovery by Dr. von Haast of the constant presence, in many individuals of dif- 

 ferent ages and sexes, of a row of small teeth of determinate number and definite 

 form, with their crowns projecting beyond the gum of the upper jaw, in a species of 

 Mesoplodon, is therefore of great interest. We have here the permanent retention 

 of a condition intermediate between that of the irregular, completely concealed, pro- 

 bably only temporary, and quite functionless teeth mentioned above and the normal 

 state of dentition of the true Dolphins; and it is especially interesting that this 

 should have been met with in a member of the genus otherwise least modified from the 

 Dolphins. I must, however, take leave to differ from Dr. Haast in thinking that it is 

 a difference of generic importance, especially as it is associated with no other structural 

 peculiarity, as far as is at present known 2 . 



These teeth, from seventeen to nineteen in number on each side, are entirely uncon- 

 nected with the bone ; and when the dense fibrous gum is removed there is no trace of a 

 socket or groove for them. They have been preserved in the specimen under description, 

 the soft coverings of the rostrum having been allowed to dry upon it. They are nineteen 

 in number on each side, and occupy a space of four inches in the middle of the rostrum, 

 the anterior teeth being seven and a half inches from the apex. The first is very 

 minute ; but they gradually increase in size to about the sixth, then remain nearly equal, 

 but diminish again, though not to the same extent, in the posterior part of the series. 

 They are slender, conical, compressed from before backwards, and incurved at the apex, 

 with sharp-pointed enamelled crowns, resembling, in fact, those of the genus Delphinus 

 in miniature. The apices of many are broken or blunted ; whether from use or after 



1 Trans. Zool. Soe. vol. viii. p. 204. 



2 Professor Gervais seems to be of the same opinion, as he says, " Mais o'est particulierenient aupres du 

 Mesoplodon soiverbense qu'il doit prendre place, et dans la range'e de dents qu'il presente dans une partie de la 

 longueur de sa machoire superieure, on ne trouverait aucune bonne raison pom- le separer generiquement de ce 

 dernier, encore moins du Doiiclwdon " (Osteographie des Cetaces, livr. xv. p. 518). 



3m 2 



