OCR Text |
Show 120 MR. A. H. GARROD ON THE MUSCLES OF BIRDS. [Feb. 3, the Psittaci (which in other points also are peculiar), and the Cucu-lina from amongst the Cuculidse, they all possess the accessory femoro-caudal (B) well developed. The semitendinosus (X) and the accessory semitendinosus (Y) are always present, and, except in Casuarius, Dromaus, and some Psittaci, the ambiens is to be found well developed. The presence of both the accessory femoro-caudal and the accessory semitendinosus (that is, of both B and Y in their myological formula) is the most characteristic feature which they have in common, giving the formula B. X Y as typical. The Anseriformes include most of the web-footed birds. Their most marked characteristic is the presence of the accessory femoro-caudal (except in Bulweria), whilst the accessory semitendinosus is absent, except in the Storm-petrels. With the exception of the Podi-cipida, the femoro-caudal is present; so that their formula is nearly always A B. X. Excluding Podiceps and a Storm-petrel in the case of one specimen examined, I have always found the ambiens present. The Ciconiiformes are less easily defined than the other groups. The caeca coli are never long ; the accessory femoro-caudal is never present; and the obturator externus is frequently more developed than in other birds, to replace it in action. It is in the pectoral region that these birds most closely agree. The strong short anterior costo-coracoid ligament, the bowed space between the superior margin of the second pectoral muscle and the furcula, and the frequently complicated arrangement of the great pectoral, whereby it is developed in a superficial and a deep layer (in which, by the way, the Procellariida agree with them), all point to a not far distant relationship. The Ardeida are the most aberrant of the order, the ambiens muscle being always absent in them at the same time that there is only one colic caecum. The Charadriiformes correspond to the Schizorhinae, so named by me on account of a peculiarity in the structure of the nasal bones, which is sufficiently special in m y estimation to justify the separation of all those birds in which it °is found into a single order by themselves. There are considerable myological differences amongst its families according to their habits, the only uniform character being the presence of the femoro-caudal muscle. The ambiens is absent in the Alcidte (Alca, Uria) and some Columba. The minor divisions of the orders above defined must now engage our attention. The order G A L L I F O R M E S may be divided into three main divisions • or cohorts-a. the Struthiones, fi. the Gallinacea, and y. the Psittaci. u. The Struthiones are peculiar in the structure of the palate ; and in them the sciatic nerve and artery always perforate the fibres of the accessory femoro-caudal in a manner not found in any other birds. They are divisible into four families, the first three of which have no oil-gland:- 1. Struthio and Rhea, which form each the type of a separate subfamily. In common they have the formula B. X Y, the ambiens muscle present, and long sacculated caeca coli, which in Struthio are |