224 MR. R. COLLETT ON HYBRID GROUSE. ._ [Apr. 20, 
EXPLANATION OF PLATE XX. 
Fig. 1. Side view of jaws of Hybodus dubrisiensis, Mackie. pg, pterygo- 
quadrate; mk, Meckelian cartilage; p, pterygo-trabecular process ; 
ot, otic process ; Am, hyomandibular ; ch, cerato-hyal. (B.M. 41675.) 
. Under view of the same: ¢wv, tuberosity on cerato-hyal. 24, natural 
transverse section of right cerato-hyal. 
. Teeth of the same, twice nat. size. 4, anterior tooth; b, hinder tooth. 
. Hyomandibular of the same, back view. 7, tuberosity. 
. Restoration of mandibular and hyoid arches of Hybodus dubrisiensis. 
. Section of the upper border of quadrate region of pterygo-quadrate of 
type specimen of Hybodus dubrisiensis, showing thickening. 
Figs. 1, 2, 4-6 are of the natural size. 
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Soe co 
4, On the Hybrid between Lagopus albus and Tetrao tetrix, 
By Rozsert Corrert, C.M.Z.S. 
[Received April 1, 1886.] 
(Plates XXI., XXII.) 
Introduction, p. 224. Young plumage, p. 251. 
Distribution, p. 225. Sex, p. 232. 
Propagation in Norway, p. 226. Supposed parentage, p. 232. 
Diagnosis and Configuration, p. 227. | Other Hybrids of Lagopus, p. 256. 
Measurements of ¢ & Q, p. 228. Habits, p. 238. 
Colouring, p. 228. Food, p. 239. 
Winter plumage, p. 229. | Skeleton, p. 240. 
Summer plumage, p. 230. 
Introductory Remarks. 
The existence in Northern Europe of two kinds of natural hybrids 
amongst the Tetraonide 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 parts of Europe, being met with 
annually in many districts, where its hybrid character is, as a rule, 
well known tothe inhabitants. This is the “ Rakkelfugl,” the cross 
between the male of Tefrao tetrix aud the female of T'etrao urogallus. 
The male of this hybrid, which has been known since 1744", in colour 
more nearly resembles the cock of Yetrao tetrir 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 nature 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 Lagopus albus, 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 Kel. Vet.-Akad. Handl. Stockholm, 1744, p. 181. 
