Zoological Society. 513 



more convex on its lateral parietes, in this respect approaching to 

 many of the Seals : the nasal bones form a broad plane, and do not 

 gradually decline, like those of the Common Otter, towards the nasal 

 opening ; they are also shorter in proportion than in that species : 

 the breadth of the nasal opening is greater than its depth, propor- 

 tions wliich are reversed in the Common Otter: the post-orbital space 

 is less contracted : on the base of the skull the space between the 

 pterygoid processes is more considerable : and the whole contour of 

 the cranium is not only broader but deeper also. The lower jaw 

 maintains the same general tendency to greater compactness, and is 

 stouter and shorter than in the Common Otter. 



Detailed admeasurements are given by Mr. Martin of the skull of 

 an individual more advanced in age than the one whose skeleton is 

 preserved, and in which the entire length of the cranium is 5 inches; 

 the greatest breadth, being across the occipital ridge behind the 

 auditory /orawiew, nearly 4 inches, the breadth between the zygo- 

 mata being the same ; the depth from the point of union of the in- 

 ter-parietal with the occipital ridge to t\\e foramen magnum, If; the 

 distance from the foramen magnum to the bony palate, 2 1-; and the 

 length of the bony palate, 2^. 



The chest is rather wide in form, but much compressed ; being 6 

 inches across at the sixth rib, while its greatest depth from the ver- 

 tebral column to the sternum is 2^ inches. The direction of the 

 ribs is obUquely backwards, and they are rather slender : their num- 

 ber is thirteen, (not fourteen, as is stated by Home,) the last five 

 being false and attached by very long cartilages to the cartUages of 

 the true ribs. 



The lumbar vertebra are six in number. 



The anterior extremities are short and small. The scapula is 3 

 inches in length and 2 in its greatest breadth : its spine is feeble 

 and but slightly elevated. The humerus is 3 inches in length : and 

 is stouter and less laterally compressed than that of a common Otter 

 of the same longitudinal dimensions. The ulna and radius are stout, 

 and are separated from each other by a greater interval than in the 

 common Otter. The paws are remarkable for their diminutive size. 

 In the common Otter, from the extremitj^ of the radius to the nail of 

 the last phalanx of the third finger the measurement is 3 inches ; in 

 the Enhydra it is 2^. 



The pelvis is long and narrow, measuring from the crest of the 

 ilium to the tuber ischii 6 inches: in the common Otter, the measure- 

 ment is but 4. The iliac bones are remarkably thick and solid, and 

 turn out from the spinal column. The distance from the centre of 

 the acetabulum to the crest of the ilium is 3 inches ; the breadth of 

 the ilium 1^. 



It is in the posterior limbs that the great power of the Enhydra 

 appears to be developed. The os femoris is short but very thick, 

 and its trochanter is bold and prominent : the trochanter minor is 

 small. The liead of the femur is globular, and is destitute of the 

 ligamcntiim teres, as in the Seals : in the Otter this ligament exists 

 as usual. The length of the thigh bone from the great trochanter 



Third .Scries. Vol. 9. No. r>7. Supplement. Dec. 183G. 3 Q 



