424 



PEOF. W. H. FLOWER ON THE GENUS MESOPLODON. 



The principal dimensions of these crania are as follows : — 



Extreme length of cranium 



Length of rostrum (from the apex of the 

 praemasilla to the middle of a line drawn 

 between the anteorbital notches'-) 



From middle of hinder edge of palate (formed 

 by the pterygoids) to apex of rostrum . . . . 



Greatest height of cranium from vertex to 

 pterygoids 



Breadth of cranium across middle of superior 

 margin of orbits 



Breadth of cranium between zygomatic pro- 

 cesses of squamosals 



Breadth between anteorbital notches 



Breadth of middle of rostrum 



Breadth of occipital condyles 



PrajmaxUlse, greatest width behind anterior 

 nares 



Prsemaxillte, least width opposite anterior 

 nares 



PraemaxUlas, greatest width in front of an- 

 terior nares 



Width of anterior nares 



Length of tympanic bone 



Greatest breadth of tympanic bono 



Mandible, length of ramus 



Mandible, length of symphysis 



Mandible, greatest vertical height of ramus . . 



M. au&tralis, 

 adult. 



inches. 



30-3 



19-9 



23-8 



11-0 



11-2 



11-7 

 7-4 

 1-7 

 3-9 



5-4 



4-4 



4-6 

 2-0 

 1-9 

 1-3 



millim. 



770 



505 

 605 



278 



283 



298 



187 



44 



99 



138 



m 



117 

 52 

 49 

 32 



M. grayi, 

 young. 



incheB. 

 30-3' 



20-2 



24-5 



10-4 



10-5 



11-1 

 7-2 

 1-6 

 3-7 



5-1 



4-0 



4.4 

 2-1 

 2-0 

 1-4 

 26-0 

 8-4 

 4-1 



millim. 



770' 



510 

 622 

 264 



268 



282 



183 



40 



95 



138 



103 



111 



53 



51 



35 



660 



214 



105 



M. hectori, 

 young. 



inches. 

 22-3 



12-6 



17-4 



9-5 



9-2 



10-2 

 5-3 

 1-5 

 3-6 



4-6 



4-2 



4-5 

 2-0 



2-1 



19-1 

 5-9 

 3-3 



millim. 



567 



320 



442 



241 



235 



259 



135 



37 



92 



117 



107 



114 

 51 



54 



484 



150 



83 



The lower jaw appears to present no differentiating characters whereby the different 

 species of Mesoplodon can be distinguished, except as regards the implantation of the 

 teeth, which will be considered presently. 



The thyro- and basihyals are present in the younger skeleton but not in the older 

 one. They are not united. In general form they resemble those of Berardius and the 

 ordinary Dolphins, presenting none of the peculiar enlargement and flattening cha- 

 racteristic of Physefer and Kogia and seen to a slight extent in Hyperoodon. The 

 stylo-hyals are preserved in both skeletons, and, allowing for difference of age, are 

 similar. They do not present the simple cylindrical characters of the same bones of 

 all the true Dolphins, and even of Physeter and Berardius, but are (especially those of 

 the older specimen) remarkably flattened and widened towards the lower end, and thus 

 approximate to the form which has hitherto been thought peculiar to Hyperoodon. 

 In M. australis these bones have a length of 5"-6 =142 millims., and a greatest 



' As the apex of the rostrum is still covered with the dried gum, this is not absolutely exact. 



- I have thus defined the commencement of the rostrum for the sake of uniformity with previous measure- 

 ments ; but, owing to the breadth of the maxilla in front of the anteorbital notches, the rostrum in Mesoplodon 

 appears to commence more than an inch in advance of the spot indicated. 



