Mr. W. K. Parker on the Osteology of Balaeniceps rex. 445 



Tetragonopterus jbneus. 



D. 11. A. 26. V. 8. L. lat. 35. L. transv. 7/6. 



The height of the body is contained three times or three and a half 

 times in the total length, and the length of the head four and four- 

 fifth times. The interorbital space is convex, and its width more 

 than the diameter of the eye, which equals nearly the extent of the 

 snout. Uniform bronze-coloured, with a brownish spot at the root of 

 the caudal. 



Hab. Fresh waters of Oaxaca (Mexico). 



in. lin. 



Total length 3 .5 



Height of the body 1 1 



Length of the head 8£ 



Diameter of the eye , 2 T 



June 26, I860.— E. W. H. Holdsworth, Esq., F.L.S., in the Chair. 



Abstract of Notes on the Osteology of Bal^eniceps 

 rex. By W. K. Parker, Memb. Micr. Soc* 



The first view of the living Balamiceps at once suggests the idea 

 of the Boatbill {Cancroma), the Heron (Ardea), and the Adjutant 

 (Leptoptilus) . Other large-headed birds occur to the mind on a 

 longer observation ; for one instinctively thinks of the Pelican (Pele- 

 canus), the Toucan (Ramphastos), the Hornbill (Buceros), and the 

 Podargus, although these birds belong to distinct and very remotely 

 related groups. Nor does the internal structure of this noble but 

 strange and weird-looking bird contradict the first external impres- 

 sions ; for the very unusual size of the head, and its great strength, 

 require certain modifications of a teleological character, such as 

 occur in the large-jawed species of other widely separated groups. 

 The difference in the structure of the skeleton between the Balceni- 

 ceps and its small New World relative, the Cancroma cochlearia, is 

 greatly exaggerated by the necessary modification of the bones in 

 the giant species, by their thickness, and by the size of the ridges 

 and out- standing processes for muscular attachment ; but the two 

 birds are, nevertheless, near allies. In the skull, especially, is this 

 difference exhibited; and any large bird may differ osteologically 

 from its small relations from this cause, much more than from any 

 necessary specific or generic distinction of character. 



Again, any peculiarity of habit in an aberrant species, or genus, 

 will make, as it were, large demands upon the structure of those parts 

 or organs which are subservient to this (as it regards the group or 

 family) eccentric mode of life. The Secretary-bird (Serpent arius) 

 amongst the Vultures, the Spoonbill {Platalea) and the Oyster- 

 catcher (H&matopus), the Pelican and the Scissors-bill (Rhynchops), 

 each form so different from its relations, are familiar instances of 

 this law. 



* This paper will be printed entire in the ' Transactions,' accompanied hy illus- 

 trative plates. 



