ALO^. 



363 



Phaleris psittacula, nice never both absent ; the formula are 

 the three following : — 



ABX- Uria. 



AX + Ceratorhina. 



AX— Phaleris. 



The biceps femoris of Brachyrhamphus gives off a fleshy 

 slip to the outside of the thigh, to the gastrocnemius (cf. 

 Podica) . This slip is not to be found in Phaleris. 



The least modified form of syrinx is seen in Alca tarda, 



Fig. 176. — Syrinx of Lomvia 



troile (aptek Beddasd). 



i, intrinsic muscle. 



Fig. 177. — Sveinx or Ceratorhina 

 monocerata (aftek Beddake). 

 iy intrinsic muscle. 



Lomvia troile, Synthliborhamphus antiquus, and Uria 

 columba. 



In Lomvia troile the last four or five tracheal rings enter 

 into the formation of a three-way piece, which is deeply 

 excavate medianly. The intrinsic muscles are attached to 

 the first bronchial semi-ring, which hardly differs from those 

 that follow ; it and the one which immediately succeeds are 

 slightly more broad than the rest. 



Alca tarda is rather more gull -like, there being no 

 marked depression in the pessulus medianly, and the trans- 

 parent membrana tympaniformis being sharply marked off 

 from a thicker yellowish region behind. 



