r02 STUDIES OF TASMANIAN CETACEA^ 



sides of the coalesced pre-frontals, that liire the back of 

 the nose. This is an ©thmo-nasal ankylosis. 



In some skulls these lateral ethmo, bony moieties, re- 

 main distinct, showing that they are not really parts of 

 the nasals ; this, however, is rare, and quite individual. 

 The rest of this cartilage, that is the central portion,, 

 may remain as cartilage throughout, or ossify to both 

 nasals, and pre-frontals. This latter is an ethmo-naso- 

 pre-frontal ankylosis. 



In Tur.nojJS, the nasals early in life remain as two- 

 bosses at the vertex of the skull, and always show this 

 basic character. Whatever may happen, later, will fol- 

 low lines well marked off from those obtaining in the 

 true Dolphins' skulls. We may cite the following, by 

 way of illustration. 



The ethmo-cartilage in skulls of Tursiops, is less com- 

 pressed than in those of Del/phinus, and in the centre it 

 may ossify as twoi tongue-like strips, that appear above 

 the upper end of the pre-frontals. These are very sugges- 

 tive of the ethmo'-turbinals, and accordingly we so nam© 

 them. We have skulls that show this very well, indeed. 

 The assumption here is, that the arrested ossific power is 

 returning to earlier evolutionary states, much in the 

 same way that Wormian ossicles appear in human skulls. 

 Exactly how much, or how little, this strip of ethmo- 

 cartilage will manifest definite ossific moieties, will de- 

 pend upon various circumstances, one of which appears to 

 be the effect of pressure. Still dealing with Tvrsio'ps, we 

 may note that the vertex of a most carefully prepared 

 skull will show the following bones, in addition to the 

 maxillse and frontals. 



1. Two ossicles that represent the Interparietal and 



Pre-interparietal. (9) 



2. The two true nasals, which combine with anv, or 



all of the other moieties in that region of the 

 skull, - according to individual, and sex varia- 

 tions. 



3. Two, Ethmo-turbinals. 



4. Two, more or less plate-like lateral moieties that 



fuse with the pre-frontals, the frontals, and 

 nasals, in various ways. These may fuse to ex- 

 tinction upon one side, and remain distinct upon 

 the other. * 



(9) Pre-interparietal not always present. 



