2^ . MK. H. o. FOBBSS OS THE [Feb. 28, 



inch \ride (measured on the upper surface), in the older specimen 

 (F) in the Otago Museum the maxUlarr ceases at 7'So inches, 

 and in the trpe ( K) at 9| inches from the apex of the rostrum, 

 so that the groove practically ceases there. The lower flange 

 of this groove b generallr traceable on the side of the rostrum 

 much more clearly than the upper, and in older specimens is very 

 pronounced at the ba.se of the rostrum, decreasing in prominence 

 as it runs forward, especially in the Kaiapoi specimen (I) and in 

 M. ausiralif. Flower. The depth of the groove and of its subtu- 

 bercular pit, and the divergence of its flanges, appear to vary with 

 age and sex, and would seem to be dependent on the indi>"idual 

 growth of the bones in the neighbourhood, especially the increase 

 forward of the palatines and pterygoids. In those forms in -which 

 the buttress is strongly developed, a shallow depression or groove 

 separates the lower flange from the maxillo-pterygoid swelling. 



Siienfrom the palatal surface. 



From this aspect the relations of the palatine and pterygoid bones 

 in the two Otago Museum specimens (A, F), in the three Canterbury 

 Museum examples (3., L K), and in M. ffi-ayi of Flowers paper 

 in the Society's Transactions are identically the same. The pala- 

 tines lie on the outside of the pterygoids, reaching forward as far 

 as but not extending beyond their pointed ends ; the pterygoids, 

 therefore, articulate directly with the niaxillaries. In the J/. (Oulo- 

 don) grayi figured by Tan Beneden the palatine bones completely 

 €urround the anterior ends of the pterygoids and extend anteriorly 

 to them, preventing their coming into contact with the maxillaries. 

 The same differences exist between the specimen in the Canterbury 

 Museum of ZijJtiug cavirosiris. in which the palatine bones sur- 

 round the pterygoids, and the figure on plate xii. his in the 

 ' Osteographie " of Van Beneden, in which they do not. The same 

 differences were also pointed out above in my remarks on specimens 

 of J/, layardi, and are therefore due solely to individual variation. 



The relations of the prema3dllaries, maxillaries, and vomer on 

 this aspect of the cranium are the same in all these specimens, 

 the amount which each contributes varying with the age, sex, or 

 individual. 



The number of teeth in the gum of the upper jaw in the examples 

 I macerated, in one case exceeded by one, in the second case was 

 less by one, and in the third equalled that given by Sir Julius von 

 Haast in describing the type species. 



The triangular pterygoid in all these examples has the usual 

 everted lower border and deep fossa, as also the deep notch at the 

 base of the pterygoid plate, and presents no essential feature by 

 which the species c-an be separated one from another. The pterygmd 

 fossae in the three specimens I dissected contained each a large 

 air-sac opening into the ear- cavity, and communicating with the 

 mouth by the Eustachian passage. In JI. gravi the pterygoid fossa 

 never extends anterior to the level of the maiUlarv tubercle. 



