310 THE PEOCEEDINGS OF THE LINNEAN SOCIETY 



side there is, first, a large flat lobe, free and notched at the 

 extremity, which overlaps the outer part of the fold of the lower 

 lip ; then there is a broad, nearly circular fold, which all but 

 surrounds the large sub-elongate nostril, then a broad lobe 

 terminating in a skinny flap, and in the middle, a thin semi- 

 circular lip, exposing completely the mass of teeth on the outside 

 of the symphysis of the mandibles. The lower lip has a large 

 elongate fold or flap on each side, while the centre, as in the 

 upper lip, exposes the front teeth. The jaws are identical in 

 form and dentition. At the symphysis they seem narrow, but open 

 out sufficiently to leave a small more or less oval space between the 

 rami, behind that the rami approach almost to touching, and then 

 gradually expand and spread outwards to the back of the mouth. 

 The teeth are somewhat pavement like, but more or less round and 

 convex, and not flat and angular, as in Myliohatis. The front teeth 

 are rather small, and tranversely ovate, in 10 rows, and in quite 15 

 series ; those on the inner series more or less tri-cuspid, according 

 to age ; those in use, or which come into contact with the teeth 

 of the opposite jaw, so far worn as only to show a transverse 

 blunt point, and the obsolete ones, on the outside of the jaw, 

 without trace of armature at all. The teeth on the hinder part 

 of the " rami " are in about eight rows, and the same number of 

 series, large, of an oblong shape, smooth, convex surface, spirally 

 disposed, and with the 4th and 5th series very large, and twice 

 as long as broad ; in young specimens the teeth are acutely 

 pointed. 



The supra- orbital ridges are elevated, are situated on each 

 side of the top of the head, and are about the same distance 

 apart as the anterior angle of the orbit is from the top of the 

 fii-st gill opening ; they can be traced in front for some distance 

 towards the snout, in a direction approaching one another, and 

 they terminate behind gradually above the first gill opening. 



The eyes are situated on the side of, but close to, the top of 

 the head, and immediately below the supra-orbital ridges ; the 

 pupil is horizontal and elliptical, with the upper surface less con- 

 vex than the lower, and the orbit is large and twice as long as 

 deep. 



