224 MR. R. COLLETT ON HYBRID GROUSE. [Apr. 20, 



EXPLANATION OF PLATE XX. 



Fig. 1. Side view of jaws of Hijbodus duhriaiensis, Mackie. jiq, pterygo- 



quadrate ; mk, Meekelian cartilage ; ^>, pterygc-trabecular process ; 



ot, otic process ; hm, hyomandibular ; ck, cerato-hj'al. (B.M. 41675.) 

 2. Under view of the same : tu, tuberosity on eerato-byal. 2 a, natural 



transverse section of right cerato-hyal. 

 .J. Teeth of the same, twice nnt. size. •7, anterior tooth; h, hinder tooth. 

 4. Hyomaudibular of the same, bock view, f, tuberosity. 

 .5. Restoration of mandibular and hyoid arches ol' Hyhodun dubrisieims. 

 6. Section of the upper border of quadrate region of pterygo-quadrate of 



type specimen of Bi/bodus dubrisicm-ii:, showing tliickening. 



Figs. 1, 2, 4-6 are of the natural size. 



4. On the Hybrid between Lagopus albiis and Tetrno tetrix . 

 By Robert Collett, C.M.Z.S. 



[Eeceived April 1, 1886.] 



(Plates XXL, XXII.) 



Litrodnction, p. 224. Young plumage, p. 2.'U. 



Distribution, p. 225. Sex, p. 2.32. 



Propagation in Norway, p. 226. Supposed parentage, p. 2;i2. 



Diagnosis and Configuration, p. 227. Other Hybrids of Lni/opu.i. p. 2.'56. 



Measurements of J & $ , p. 228. Habits, )). 2.38. 



Colouring, p. 228. . Food, p. 239. 



Winter plumage, p. 229. Skeleton, p. 240. 



Summer plumage, p. 230. 



Introchictory Bemarks. 



The existence in Northern Europe of two kinds of natural hybrids 

 amongst the Tetraonidse was already known in the last century, 

 and one form of these is rather common in the forests of Norway and 

 Sweden, as well as in some other ])arts of Europe, being met with 

 annually in many districts, where its hybrid character is, as a nde, 

 well known (o the inhabitants. This is the " Rakkelfugl," the cross 

 between the male of Tefrao tetrix and the female of Tetrao vrogallus. 

 The male of this hybrid, which has been known since 1/44', in colour 

 more nearly resembles the cock of Tetrao tetrix than that of 

 Tetrao urogallus, whilst the female in this respect is less charac- 

 teristic and resembles the hens of both species. In shape its 

 hybrid mature is indicated by the form of the tail ; in size it is 

 intermediate between both parents, so that both sexes are larger than 

 the father, and the male is even larger than the mother. 



The other hybrid, the result of a connection between Tetrao tetrix 

 and Lngojivs albvs, which is called in Norway and Sweden " Rype- 

 Orre," is much rarer, and specimens are still desiderata in most 

 museums. The origin of this hybrid, its habits, and its places of 

 resort are as yet partially, if not wholly, obscure. Its winter plumage 

 is the only one which is generally known, whilst the spring or 

 summer plumage is all but unrecorded. 



1 Kgl. Vet.-Akad. Handl. Stockholm, 1744, p. 181. 



