2 20 SiiUFELDT OH tJic Ostcology of Cluclus MexlcaNns. 



from the shaft in the adult, very niucli as I fi^^ured thcin in 

 Laniiis. 



Such of my readers as have read mv account of the develop- 

 ment of Centrocerctis in the Osteology of the Tetraonidce. will 

 remember what we had to say in regard to the lower end of the 

 tibia and its growth, and also all that Professor Morse has done 

 for us in that direction. The specimen we have of the 30ung of 

 Cinclus does not admit of the demonstration of the intermedi- 

 um; \h(ijil)?ilare and the tibiale seem to ossif\' separately, how- 

 ever. We must admit, then, that in this instance we are no nearer 

 solving the problem of the homologies of the avian tarsal seg- 

 ments than we were before, but a little light at least is thrown on 

 the subject when we come to examine tlie next bone, the tarso- 

 metatarsus. 



In nearly all birds this bone has at the back part of its upper 

 end a tuberous process, amalgamated with the shaft in the adult, 

 that assimies various forms in different members of the class. 

 This bony process has long been regarded with suspicion, as to 

 whether it was one of the ankle or rather tarsal bones or not. 

 Let us hear what a few of the authorities have to say in this 

 matter. Professor Owen tells us in Vol. 11 of his Anatomv of 

 the Vertebrates, when speaking in general terms of this process, 

 that : "One or more longitudinal ridges at the back of the upper 

 end of the metatarsal are called 'calcaneal' ; they intercept or 

 bound tendinal grooves w'hich, in some instances, are bridged 

 over by bone and converted into canals ; the ridges may be ex- 

 panded and flattened." This would lead one to think that the 

 Professor inight regard this process as the homologue of the os 

 calcis, a tarsal bone. 



Professor Huxley, in his Anatomy of Vertebrated .Vnimals, 

 page 254, tells us, in speaking of this process, that: "Again in 

 most birds, the posterior face of the proximal end of the middle 

 metatarsal, and the adjacent surface of the tarsal bone, grow 

 out a process, which is commonly, but improperly, termed "cal- 

 caneal." The inferior surface of this hypo-tars7is is sometimes 

 simply flattened, sometimes traversed by grooves or canals, for 

 the flexor tendons of the digits." 



Mivart says, when referring to birds: "Thus no projection 

 corresponding with the tuberosity of the os calcis exists in this 

 compound bone." (Elementary Anatomy, p. 206.) 



