1874.] MR. A. H. GARROD ON THE MUSCLES OF BIRDS. 121 



situated peculiarly far from the cloaca. There is no aftershaft to the 

 contour feathers. Struthio has two carotids, Rhea only the left. 



2. The genera Casuarius and Dromceus. They have the formula 

 A B. X Y and B. X Y respectively. The ambiens muscle is absent, 

 the caeca coli are short, and there is a very large aftershaft to the 

 contour feathers. There are two carotid arteries. 



3. Apteryx, hi which there is an extra femoro-caudal muscle, the 

 formula otherwise being A B. X Y. The ambiens is large ; the cseca 

 coli are well developed ; and there is only one carotid, the left. 



4- The Crypturi, with a formula A B. X Y. The ambiens muscle is 

 large ; the cseca coli are well developed ; and an oil-gland is present, 

 well tufted. The aftershaft may or may not be present on the 

 contour feathers. 



/5. The Gallinacece all comprise B. X Y in their formula ; the 

 ambiens is present in all ; and except in the Musophagidce there are 

 always caeca to the intestine. 



They are divisible into six families : — 



1 . The Palamedeidce, with formula A B. X Y, the ambiens present, 

 caeca sacculated as in Struthio and Rhea only, two carotid arteries, 

 no aftershaft or a very small one, and a tufted oil-gland. 



2. The Gallince, with formula A B. X Y or B. X Y. The ambiens 

 is always present, as are caeca coli, an aftershaft, and a third pectoral 

 muscle beneath the second ; the oil-gland may be strongly tufted, or 

 the tuft may be very weak ; in the Megapodidce it does not exist. 

 The second pectoral is very long ; and there is a characteristic shape 

 about the sternum. In the Megapodidce there is only one carotid, 

 the left ; in all the others both are present. Neither Turnix nor 

 Pterocles are included in this family. 



3. The Rallidce, with formula A B. X Y, the ambiens and caeca 

 present, two carotids, an aftershaft, a tufted oil-gland, and a charac- 

 teristic sternum. Parra is not included. 



4. The Olididce, including the Otidince, (Edicnemus, Serpentarius, 

 and Cariama (and perhaps the next genus, Phomicopterus). The 

 formula is B. X Y ; the ambiens and caeca are present, as is the after- 

 shaft ; there are generally two carotids, though in Otis denhami the 

 right only is present, and in Tetrax the left ; the oil-gland when pre- 

 sent, as in all but Otis, is tufted, except in Cariama and Chunga. 



5. The Musophagidce, with formula A B. X Y, an ambiens muscle, 

 two carotids, an aftershaft, a tufted oil-gland, and no caeca. 



6. The Cuculidce, with an ambiens muscle, two carotids, nude oil- 

 gland, and casca. They form two subfamilies : — 



The Centropodince, or Ground-Cuckoos, with formula AB. X Y. 



The Cuculince, or true Cuckoos, with formula A. X Y. 



y. The cohort Psittaci presents in many points intermediate cha- 

 racters between the homalogonatous and the anomalogonatous birds. 

 With a constant formula A. X Y, no caeca or gall-bladder, an oil- 

 gland tufted or absent, the ambiens may or may not be present, and 

 the carotids may exhibit peculiarities in their arrangement*. 



The order Anseriformes may be divided into two cohorts — «. 

 the Anseres, (j. the Nasutce. 



* See P. Z. S. 1873, p. 465. 



