URTA TROILE. 381 



or what might be called its patella, or what answers to the patella in 

 other birds. This bone projects up in the line of the tibia, 2 inches 

 beyond the joint of the knee : there are three strong muscles inserted 

 into it, one of which is inserted through its whole length ; the other 

 two nearer to the joint of the knee : these muscles arise all along the 

 sides-man or ileum : they must give great power to the forward motion 

 of the leg, although they must lose in velocity. This projecting 

 process gives a greater surface of origin to the extensors of the tarsal 

 bone, or what is commonly understood by the leg, than they otherwise 

 could have had; for some of those muscles arise from its fore-part 

 through its whole length, and wind round the tibia to get behind the 

 tarsal joint. The tarsal bone, or what is called leg, is very thin, having 

 its sides outwards, and its edges turned forwards and backwards. This 

 form may be against the effect of the back-stroke, but it assists in the 

 fore, or the bringing the leg forwards 1 . The back-toe is small, but it 

 is webbed with the outer toe of the foot. The first bone of the three 

 front toes is articulated almost in a straight line with the bone of the 

 tarsus, and the second bone only extends a little forwards, so that the 

 bird cannot possibly walk ; and when it floats on the water its legs and 

 toes are in a straight line along the belly. 



The Diver, or Sea-Parrot [Fratercula arctica, Brisson] . 



This bird has an orange bill and legs, back black, breast white. 

 What is called thigh, but more properly leg, is close to the body, and 

 passes backward in the direction of the body, as far as the extremity of 

 the rump. This part of the leg is not so much detached from the body 

 as in other birds. 



The stomach is a kind of gizzard with a strong transparent horny 

 coat. The duodenum is as usual: the other intestines make several 

 turns, and pass down or back, to form the rectum : there are two small 

 caeca. [In the cloaca are] two small nipples, which I suppose to be 

 the terminations of the vasa deferentia, like those in the cock. The 

 oesophagus enlarges before it enters the thorax. 



The Sea-Parrot [Uria Troile, Latham]. 



This bird is web-footed, but has no back-toe : it is black. The bill 

 is something like the vultures, being covered with feathers as far as the 

 nostril : where the feathers terminate, there is a round bend or ridge 

 with a pretty deep groove : a little further on there is a hollow that 



[Osteol. Series, No. 1166.] 



