304 NORTH AMERICAN MUSTELID.E. 



together frequentl}' sufficient, in old individuals, to lock tbe 

 jaw. Tbe posterior nares are only separated by a vertical 

 median septutu for a short distance ; they debouch together at 

 the edge of tbe bony palate as a single oritice, as in Mustelidce 

 generally, but not as in Taxldea {q. v.). The bullae ossese are 

 liattish, about as in MephiUnxv, strongly contrasting in this re- 

 spect with MiLstelince and Melhue. They are most vaulted at 

 the antero-internal angle j exteriorly they are produced into a 

 long slender tubular meatus. The basilar space betwixt these 

 periotic bones is very broad, with its sides little convergent 

 anteriorly. The foramen lacerum posterius sometimes appears 

 as several distinct circular foramina through which the cranial 

 nerves respectively emerge separately, a state I have not noticed 

 elsewhere in the family, though it may occur ; it is analogous 

 to the division of the anteorbital foramen frequently seen in 

 the Skunks. This state of the lacerate fissure is usually un- 

 symmetrical; that is, it is not alike on both sides of the same 

 skull. 



The bones of the skull are early confluent in Lutra. Thus 

 even the nasal sutures, usually among the most persistent in 

 Mustelidce^ are obliterated at an age when the skull is still thin 

 and papery. In a very young specimen in which the bones are 

 still mostly distinct, I observe the following disposition of the 

 sutures: The nasals are received behind in a shallow semi- 

 circular recess of the frontal; their sides are approximately 

 parallel; the intermaxillary and maxillary form each about 

 half of the rest of the nasal boundary. The maxillary ends 

 about opposite the middle of the orbit ; there is but a beginning 

 of wedging of a process of the frontal between the nasal and 

 superior maxillary (cf. Taxidea). The coronal suture is ex- 

 extremely irregular ; it lies altogether back of a line drawn 

 across the apices of the coronoid processes when the jaw is in 

 situ. Nearly all the dome of the cranium is parietal, the 

 squamosal forming only a low irregular border along the side, 

 not a fourth of an inch above the root of the zygoma, though it 

 occupies much surface beneath the skull. Owing to the width 

 of the glenoid, it is entirely separate from the sphenoid. The 

 occipital crest is also chiefly parietal, as the lambdoidal suture 

 passes across it to gain the back aspect of the skull at a point 

 nearer to the median line than to the mastoid. The latter is a 

 sizable element, wedged between the parietal and squamosal 

 above, periotic below and in front, and a small piece of the 



