DK. J. MUEIE ON THE ANATOMY OF THE SEA-LION. 517 



constricted X-position to one another, or together are semirotated, lying slanting 

 inwards on their short axes. These anomalies have a most important bearing, inasmuch 

 as mechanism for swimming and diving are concerned : and they well explain, religated 

 with musculo-tendinous 1 accessories, how it is that the hind foot acts like a pivot on 

 the heel when walking or running. It is in fact an adjustment of instrument for 

 terraqueous locomotion. The awkward pedal defect colloquially known as " flat-footed " 

 in man is a kind of first stage towards the Otary's condition, though through ligamen- 

 tous rather than osseous conformation in his case. The Earless Seal's incapacity to use 

 the hind foot on land depends more on the different proportion of femur to leg-bones, 

 and lowered attachment of tegumentary caudal expansion, than to absolute difference 

 in the construction of the bones forming the ankle-joint. In the Sea-lion the cuboid, 

 naviculare, and entocuneiform are each fair-sized, the meso- and ectocuneiform small 

 and very much laterally compressed, particularly the latter, which is indeed a diminu- 

 tive bone. 



With respect to the metatarsals, the hallucial is longest and strongest, the fifth a 

 shade less, the three intermediate much slenderer and a trifle shorter. Not taking into 

 account apical cartilages, the bones of the digits terminate somewhat subequally — the 

 first, however, being shortest, the fifth next, and the third by a grade the longest. It 

 results that the three middle digits have altogether the longest phalangeal bones : but 

 the proximal phalanx of the hallux is in itself decidedly the longer and stouter bone 

 compared with the proximal of the other digits. The second, third, and fourth ungual 

 projections are best marked. 



II. The Nervous System. 



1. Remarks on the Extraction of the Brain and Membranes. 

 The strong fibrous pericranium having been divided, the bone of the cranial vault 

 was carefully sawn through in a nearly horizontal line, extending on each side from the 

 upper arch of the foramen magnum forwards, close to the postfrontal prominence. 

 At the latter part the saw was again used vertically and transversely, so as to cut 

 the anterior points of the horseshoe-shaped horizontal incision. When the calvarium 

 had thus been loosened in its osseous circumference, it still remained firmly fixed by 

 the bony tentorial lamella. This latter was then broken through by manoeuvring 

 in a wriggling manner backwards and upwards, and the brain-pan removed. The 

 great difference between the thick osseous protection afforded to the cerebral mass 

 above, and the thin side walls, became strikingly evident on the calvarium being raised 

 (see figs. 9 and 10). It would appear as if the powerful temporal and masseter muscles, 

 besides being massive fleshy engines of mastication, must also, with their fatty and 



1 For corroborative testimony refer to the various paragraphs in pts. i. & ii. of these researches, on the 

 Walrus and Sea-Lion. 



vol. vin. — part ix. June, 1874. 4 c 



