R.-J. ANDERSON — CETACEA 707 
the occipital condyles and the condition of the premaxillæ, which pre- 
sent an appearance somewhat like the palatine portion of the vomer 
in some Crocodilia, and have a position like that of the dumb—bell bone in 
Ornithorhynchus—may be here alluded to. FLower mentioned that the 
external bony nares of the Elephant, especially the young Elephant, were 
in position like similar openings in Cetacea. À comparison of the Meso- 
plodon and Cetacean skulls seems to bear out the suggestions of FLowERr 
and others that Cetacea and Sirenia are related to the Ungulates or rather 
to the Elephantine group, « albeit very far back » (Lynekker). The for- 
mation and mucous membrane of the mouth and the edentalous jaws 
suggest a resemblance to the Bovidæ. The large cerebral cavity reminds 
one of the cranial cavity in Proboscidea!. The anterior nares look up and 
are far back in the proboscidean and this holds decidedly for Mesoplodon. 
The rostrum is greatly developed in the latter (in the adult state). 
In the Elephant and Dugong however this structure, though short, is 
thick and solid and gets always a special description. The incisor teeth 
demand a larger supporting bone mass, and it is possible that the disap- 
pearance of these teeth may nave led to elongation of the snout by a 
bony deposit. The figures given of a fossil Elephantine skull preserved 
in the Museum d'Histoire naturelle at Paris seem to show that some 
ancient proboscidean groups had trunks intermediate in size between 
Elephants and Tapirs and one of these which had two tusks in the lower 
jaw may be taken as one of the nearest relatives, in the Elephantine 
group, to the ancestors of Mesoplodon. It is probable (possible) that the 
factors that produced the primitive form of trunk in an Elephant pro- 
duced a cylindrical rostral groove ina Wesoplodon. The miniature tusks 
in the lower jaw of the latter look like the shrunken tusks in lower jaw 
Of Deinotherium. The Dugong seems more closely connected with the 
parentage of the Elephant?. The incisors, premaxillæ, aborted nasals, and 
rostrum all point to relationships with Elephants and whales, besides 
the placentation, the position of Mammæ and the succession of the mo- 
lar teeth high up, in the forms. The premaxillæ in these three groups 
reach high up, (the frontals in Dugongs or Elephants), and the maxillæ 
although less, massive in Mesoplodon for want of teeth are in Orca and 
Globiocephalus strong, whilst in the latter the extension of the tooth 
cases upwards or downwards shows how a composite tooth may lead to 
separate and smaller teeth. The large maxillæ in the Proboscideans 
(Elephants) are due to the formation and extension of the great compo- 
site molars. This leads to a shrinkage of the alisphenoids and indirectly 
to shortening of the parietals, below and in front, for the squamosals 
! KükewrHaLs brain weights of Cetacea may be compared with that of Elephant. 
?2 WoopwaRD and ANDREWS. 
