638 iiti. F. fi. beSdAkd on TUB [-^pr. 21, 



6. On the Anatomy of a Grebe {^chmophorus major), 

 with Remarks upon the Classification of some of the 

 Schizognathous Birds. By Frank E. Beddard, M.A., 

 r.R.S., Prosector to the Society. 



[lleceivod March 17, 1890.] 



As BO few of the Grebes have been dissected, I took the 

 opportunity offered, by the death some months suice of a specimen 

 of ^climophoi-us major, to make some notes upon the principal 

 viscera and muscles, which 1 now lay before the Society. 



As is well known, birds differ very much in the extent of a 

 horizontal membrane which is attached laterally to the oblique 

 septa and posteriorly and ventrally to the abdominal wall. This 

 membrane has been variously termed " Omentum," " Pseudepi- 

 ploon," and " Horizontal septum." When the abdominal viscera of 

 the Grebe are exposed by cutting carefully through the body-wall 

 at some distance behind the sternum, the cavity which contains 

 them is seen to contain only the intestines. As is the case with 

 many other birds, with many Passeres for instance, the duodenal 

 loop is very extensive, reaching right to the end of the abdominal 

 cavity. This cavity, containing the intestines, is shut oif from the 

 anterior part of the abdominal cavity by an almost vertical septum, 

 whichisthereduced equivalent of thehorizontal septum. This septum 

 cuts off from the intestinal cavity another cavity which incloses the 

 gizzard and the liver, and is again divided into right and left halves 

 by the falciform ligament. The right cavity thus formed contains 

 as usual only the i-iglit lobe of the liver. I should mention also, 

 ai a fact of some systematic importance, that neither the gizzard 

 nor the entire extent of the liver is sheltered by the sternum ; 

 they lie nearly altogether behind it. In this particular JEelmiopliorus 

 differs from Psoplda, Cariama, and the EallidiB ; but the Grebe 

 agrees with those birds as well as with the Ducks in the small 

 extent of the horizontal septum. 



§ Myology. 



I have only made notes upon the more important muscles from 

 a classificatory point of view. 



The iirrangement of the tendons of the tensores patcuiii is 

 characteristic. The tensor brevis is early divided into two separate 

 tendons which run down the patagium to be inserted as usual on 

 to the forearm. They do not, however, as in the majority of birds, 

 form well-defined narrow tendons, but are thin and ill-deiined 

 sheets of tendon. The division which lies nearest to the humerus 

 is particularly thin and difficidt to delimit. The outer band has a 

 thickened strand on the side nearest to the humerus ; it thins off 

 gradually on the outer side. The nerve to tlie hand passes under 



