AND MESOPLODON SOWERBYI. 763 



than the left, and its inner surface was directed forwards and inwards, whilst that 

 of the left was more vertical, and to a great extent directed inwards. The upper 

 end of the right bone mounted also higher than that of the left, and formed a 

 thick and strong lobed projection, which overhung the pre-nasal fossa and the 

 orifice of the right nostril. The summit of the left bone was thinner, less curved, 

 less projecting, and more ridge-like than lobed. A nervo-vascular canal of some 

 size opened on the inner concave surface of each pre-maxilla, about 4 inches 

 behind the posterior end of the meso-rostral bone. 



The meso-rostral bone formed one of the most characteristic features of the 

 skull. It occupied the interval between the anterior ends of the pre-maxillse. 

 Near the tip it was narrow, and so intimately blended with the other bones of 

 the beak, that a faint superficial groove on each side was the only indication 

 of their original separation. But where the pre-maxilke began to diverge, then 

 the meso-rostral bone dilated to a thick dense bar, 2-| inches wide in its greatest 

 transverse diameter, which extended backwards to 1 3j inches behind the tip of 

 the beak. At the same time, the grooves marking its separation from the pre- 

 maxillse increased in depth and breadth, more especially on its left side. Hence 

 this bar was not absolutely mesial, but had a slight inclination to the right 

 side. At its hinder end it abruptly ended in an almost vertical, truncated 

 smooth face, which became continuous with the vomer, where that bone formed 

 the floor of the hollow of the beak. There can be no doubt but this bar 

 rested on the anterior part of the vomer, and was anchylosed to it. At the tip 

 of the beak the meso-rostral bone seemed as if subdivided into two lateral 

 halves by a longitudinal cleft, but I am inclined to think that this cleft was 

 rather to its left side, and marked the separation of the bar from the left lateral 

 half of the vomer, the separation of which, again, from the corresponding pre- 

 maxilla was indicated by a shallow groove. 



The two nasal bones were situated between the summits of the two pre- 

 maxilfce, and presented flattened surfaces superiorly. They were inclined for- 

 wards and to the left, and, with the lobe of the right pre-maxilla, overhung, like 

 the eaves of a house, the apertures of the nose. They were firmly anchylosed to 

 each other, to the frontal, pre-maxillse, and mes-ethmoid, and only faint traces 

 of the original sutures remained. The right nasal, which was rather the longer 

 of the two, was 6 inches in its antero-posterior diameter, by 1^ inch in its trans- 

 verse diameter. 



The mes-ethmoid portion of the nasal septum was curved to the left, so that 

 the nasal fossae were unequal in size, the right being 2§ inches in antero- 

 posterior, and 2 inches in transverse diameter ; the left being 2| inches in 

 antero-posterior, and only If inch in transverse diameter. The upper border 

 was sharp, and prolonged into a spine at its junction with the anterior border. 

 The anterior border expanded into a smooth surface If inch broad at its greatest 



VOL. XXVI. PART IV. 9 N 



