1876.] MR. DRESSER ON THE BLACK AND HAZEL GROUSE. 345 



1 1 inch high, covered at its blind end with the crypts of shallow 

 glands, which also run down its sides. That it is a modification of 

 the bursa Fabricii cannot he doubted. 



EXPLANATION OF THE PLATES. 

 Plate XXVI. 

 Fig. 1. View of left side of neck of Plotus anhinga, dissected, l.c.a. longus 

 colli anterior muscle ; l.c.p. longus colli posterior muscle. The fibrous 

 representative of Donitz's bridge is seen attached to the ninth cervical 

 vertebra. 

 2. View of part of the posterior region of the neck of Plotus anhinga. The 

 roman figures refer to the cervical vertebras counted from the head. 

 Donitz's bridge is seen attached to the ninth; and at a is also seen a 

 fibrous band, which is of similar function, attached to the eleventh. 

 At b is seen the fasciculus of the tendon of the posterior neck-muscle 

 which traverses the fibrous loop, which latter has been removed on 

 the left side. 



Plate XXVII. 

 View of the anterior thoracic region of Plotus anhinga, dissected to show 

 the superficial (p 1,1) and deep layer (j). 1, 2) of the pectoralis major 

 muscle on the right side, as well as the pectoralis minor (p. 2) on the 

 left. The insertion of the deeper layer of the pectoralis major is seen 

 to be surrounded by the much more considerable mass of the similar . 

 portion of the superficial stronger layer. The triceps (t) and the 

 biceps (//) of the cubitus are seen on the right side, as is the patagial 

 slip (b. s) of the latter. The sternum (st.) is superficially bound to 

 the lower end of the coracoid bone by the anterior sterno-coracoid 

 ligament {ant. st. cor. lig), which is particularly powerful in the Ste- 

 ganopods and Storks. 



Plate XXVIII. 

 Fig. 1. View of top of head of Plotus anhinga, showing the occipital style (a) 

 and the temporal muscle (t) arising from it on one side. 



2. Stomach of Plot us anhinga, inside view. 



3. Anterior view of the lower end of the trachea in Plotus anhinga. 



4. The same in Sula bassana. 



5 & 6. Top and side view of the patella in Pkalacrocorax carbo, showing 

 the canal for the ambiens muscle. K.B. The side view (fig. 6) is acci- 

 dentally drawn with the base uppermost. 



7. Front of patella in Plotus anhinga deeply grooved by ambiens muscle. 



2. Remarks ou a Hybrid between the Black Grouse and the 

 Hazel Grouse. By H. E. Dresser, F.Z.S. 



Amongst the Gallinaceous birds, and especially amongst the 

 Ducks, we not unfrequently find wild hybrids ; and not a few of 

 these hybrids have during the last year or two been exhibited at the 

 meetings of this Society — but none, I may almost venture to say, so 

 interesting as the bird I have now the pleasure to exhibit before the 

 meeting ; for there can be no doubt that it is a wild cross between 

 the Black Grouse (Tetruo tetrix) and the Hazel Grouse (Bonasa 

 betulina), a cross that has, so far as I can ascertain, never yet been 

 recorded. The Rackelvoyel of the Swedes, the hybrid between the 

 Capercaillv and the Black Grouse, is by no means uncommon, 

 especially in places where the males of the Capercailly have been 



