Otter of Central America. 619 



3. M. 1 sup. is, as in enhydris, more extended trans- 

 versely ; in canadensis it has a more quadrate sliape, and is, 

 besides, as a rule, distinguished from both bj a nick in its 

 posterior border. 



In the relative dimensions of the skull annectens presents 

 intermediate characters : — Absolute basal length : canadensis 

 95'8 (?) — 103'4 millim.; annectens 97'8 . 106*2; enhydris 

 93—115*. 



Greatest breadth (percentage dimensions) : 



canadensis 69-1 — 78"1 



annectens 75 . 75'1 



enhydris 67'1 — 77 



Cranial breadth, behind zygomatic arches and above 

 meatus audit, (pc. dim.) : 



canadensis 55'3 — 56- 1 



annectens 58'3 . 59"8 



enhydris 55'1 — 61 



Breadth between upper canines (pc. dim.) : 



canadensis 243 — 27"2 



annectens 26-1 . 28'2 



enhydris 24-5—28 



Palate length (pc. dim.) : 



canadensis 466 — o05 



annectens 459 . 46 5 



enhydris 42*9 — 54'6 



In the greatest posterior breadth — as in the form and 

 position of premolars — the Central-American Otters present 

 features of their own, since they show the maximum of 

 posterior breadth of all the crania under consideration : 



annectens 72'7 . 74'5 



canadensis 637 — 69 



enhydris 625— 71 



The Central-American Otters, therefore, whilst sharing 

 some characters with canadensis, on the whole approach more 

 to enhydris. Besides, some of their characters are inter- 

 mediate between the North-American and the South- 

 American Otters ; so that, even aj)art from their habitat, 

 they are in more tlian one sense intermediate between their 



* It must be confessed that my material of canadensis ia sadly insuffi- 

 cient ; the ten skulls of enhydris, of which all the measurements could 

 be taken, give much better averages than the five of canadensis. 



43* 



