No.2.] SHUFELDT ON NORTH AMERICAN TETRAONIDJS. 347 



of bone that usually meets the shaft at juuction of upper and middle 

 thirds, oceasioually running further down to become confluent with it in 

 every instance ; this feature is rarely present in the Quails. In Centro- 

 cercus and others the hinder aspect of the tarso-meta tarsus is sharply 

 marked by muscular ridges. The superior and articulating surface of 

 this bone displays eminences and depressions fashioned to accommodate 

 themselves to the condyles of the tibia ; a tuberosity on the anterior mar- 

 gin in the articulated skeleton fits into the intercondyloid notch of the 

 bone. Below this the shaft in front is scooped out, having at the base 

 of the dejiression two small elliptical foramina, side by side, and to the 

 inner side of its boundaries one or two pointed muscular tubercles. The 

 distal and transversely expanded end of the bone presents the foramen 

 for the anterior tibial arter3^, occupying its usual place, and the three 

 trochlear apophyses for the toes, the middle one being the largest and on 

 the lowest level. The two lateral ones, separated by wide notches from 

 the former, are thrown but a limited distance to the rear, so that the 

 concavity behind them is not peculiar for any great amount of depth. 



The OS metatarsale accessor ium is situated rather high uj)ou the shaft, 

 and bears more than an ordinary semblance to a demi-phalanx, with its 

 distal articular trochlea. As usual it is freely attached by ligaments. 



The internodes are based upon the more common plan as applied to the 

 avian foot; i. e., in the order of the phalanges, from the first to the 

 fourth, 2, 3, 4, 5 joints, and of such a pattern they are markedly typical, 

 and justly equipoised for the size of the bird. 



They possess the usual enlarged and biconcave proximal extremities, 

 with the distal and convex bi-trochlear ends, with a more or less subcylin- 

 drical shaft ; the ungual joints being but moderately curved downwards. 



There are but few or no striking differences to be noted as existing 

 among the lower extremities of our Tetraonidw. 



The bones are very delicately fashioned in Tetrao canadensis and the 

 Sharp-tailed Grouse ; that is, the calibres of their shafts seem to be less 

 as comi)ared with their general lengths, but they belong, we must remem- 

 ber, to very trim little game birds, as contrasted with our heavy and 

 ponderous old Sage Grouse of the western prairies. Our specimens of 

 Lagopus and Tetrao ohscurus do not show the bony extension from the 

 tendinous process at the back of the tarso-metatarsus, apparently present 

 in all the others and alluded to above — Centrocercus sometimes proving 

 an exception — and this bone never normally develops a spur in any of 

 our North American Grouse, as seen in birds of near kin. 



Tendons of the anti-brachium and pinion are very prone to ossify, and 

 one is quite constant on the anterior aspect of the metacarpus. This 

 applies with still greater force to the lower limb, where it seems that 

 every tendinous extension of the muscles of thigh and leg become bone 

 for their entire lengths, then forking sometimes over the fore part of 

 tarso-metatarsus as they branch to be distributed to the podium. 



It may be found that Bonasa can claim normallj' six segments as rep- 



