112 peof. w. b. ben ham. o>~ the [May 2! , 



tubes, most of which lie behind the chamber itself. These tubes, 

 as well as those that are in connection with the canal itself, are 

 similarly lined with a greyish membrane. 



On the floor of the chamber, towards the median line, is a 

 prominent aperture, somewhat curved, and provided with raised 

 black lips. I took this, at first, for the true right nostril, but, for 

 reasons given below, this is probably not the correct interpretation. 

 This aperture leads into a short canal, curved towards the right, 

 and then bending backwards towards the left, which in its turn 

 opens into a lower and larger spiracular chamber 1 . This lower 

 chamber (PI. IX. fig. 7, B) rests, by its posterior wall and its sides, 

 against the bones of the cranial region of the skull ; its anterior 

 wall (S), however, is soft, reddish, thick and muscular, and is 

 evidently capable of considerable movement. The chamber is 

 irregularly pyriform, the dorso-ventral diameter being much greater 

 than its transverse diameter ; it is, too, wider near the dorsal than 

 at the ventral end. The longer axis is not truly dorso-ventral, but 

 is somewhat oblique, the lower end being slightly more forwards 

 than the upper, which is situated behind the upper chamber (see 

 diagram, PI. IX. fig. 9). The roof is concave and asymmetrical ; the 

 anterior and posterior walls meet below at an angle, where it is 

 apparently closed ; but in the middle of the angular furrow the 

 reddish colour of the anterior wall becomes feebly pigmented with 

 black, and here, by closer inspection, is to be found a very small 

 aperture — about | inch in diameter — which leads by a short canal 

 into the nasopalatine canal (PI. YIII. fig. 5,j; PI. IX. fig. 9, c). 



It is stated by Owen, in his ' Comparative Anatomy,' that the 

 right bony canal in the skull does not transmit a narial canal : this 

 is an error (which may probably have already been pointed out). 

 The right narial canal is perfectly evident, though much smaller 

 than the left one. 



This lower chamber (PI. IX. figs. 7, 9, B) is about twice the size 

 of the upper chamber, or even greater ; but I omitted to make a 

 note of the dimensions. It is lined by a membrane that differs in 

 character in the anterior and posterior walls. The former is lined 

 by a smooth, reddish " mucous membrane," the latter and the sides 

 and roof are covered by a shining, grey, tough membrane, covered 

 with small closely-set papilla?, which I at first mistook for some 

 kind of parasite. 



These papillae (PI. IX. fig. 8) are vascular. Each is short and 

 somewhat club-shaped, measuring i inch in height by ^ inch 

 across. They are most numerous, and quite densely aggregated, 

 on the roof, and the upper part of the hind wall and sides : lower 

 down they become sparser (in the drawing they are not represented 

 in their true abundance). 



The junction of the side walls with the back of the chamber 

 is crossed by a number of narrow tendinous strands, some 

 of which are covered with papillae. The microscopic structure of a 



1 This short canal has been severed, but no part appears to have been 

 removed. 



