546 ON TKE ANATOMY OF ^CHMOPHOBUS MA.TOB. [Apr. 21, 



and to the Plovers being only seen in one species of each group and 

 in the aberrant Ehyncliops. There is, moreover, the same amount of 

 likeness 1 o the Limicolas proper in a small point which may be regarded 

 as of equal importance. The biceps slip, always present in theAlcidte, 

 has, at least as n rule, rather unusual relations. Thus in Alcu 

 tonhi Piirbringer figures it as attached partly to the patagial 

 raembrnne and partly to the inner of the two brevis tendons. In 

 the Gull the insertion is the more normal one, i.e. on to the longus 

 tendon. In Fratercula arctica the muscle is inserted upon the 

 middle of the three brevis tendons. Now in a specimen of TmujU 

 canutus (doubtless individual variation), I found a second biceps 

 slip in addition to the usual one, which was inserted on to the outer 

 of the two brevis tendons. This tendon I take, for reasons already 

 explained, to correspond to the middle of the three tendons of 

 Fratercula. 



I have carefully studied the windpipe of a number of Auks, and 

 can find no reasons for associating them especially with the Gulls 

 from an examination of this organ. The syrinx is seen in its most 

 characteristic, even exnggerated, form in Ceratorliina monocerata. 

 In this Auk (fig. 6) the first bronchial semiring is the shape 

 of half an ellipse — a gross exaggeration of the generally arched 

 form of this ring in the avian syrinx; the same form is shown by 

 the second bronchial semiring, wliich lies as it were inside tlie first 



Fig. 0. 



Pig. 6. — Syrinx of Ceratorkina monocerata : i, intrinsic muacles. 

 Fig. 7. — Syrinx of Lornvia troile : i, intrinsic muscles. 



and is concentric with it. The intrinsic muscles are attached to 

 the first. Nothing of this kind occurs in any Gull or Limicoline 

 bird known to me. In other Auks, however (fig. 7), the syrinx 

 is decidedly more typical in form. It is an interesting fact 

 thot we can arrange the family into two subfamilies according to 



