352 Descriptions of the Groups of Birds 



With regard to the Cantrices, I would particularly insist 

 on the relative or mutual independency of those structural 

 characters which I have indicated as constant: viz. the pe- 

 culiar sternal conformation, and complex vocal apparatus, the 

 small intestinal cceca, and high cerebral developement: either 

 of the two first of which characters is only found accompani- 

 ed by all the others. These coincidences in different systems 

 of organs, which in no degree necessitate each other, furnish 

 the most satisfactory and conclusive proof of the naturalness 

 of this comprehensive division. 



I proceed now to treat on the successive groups of Hetero- 

 genes ; which, for the avoidance of unnecessary repetition, I 

 prefer to commence with the rollers, bee-eaters, and kingfish- 

 ers, — three nearly allied, but separate and distinct families, 

 which combine several characters of the todies and jacamars, 

 with others of the hornbills and of the hoopoes. 



We perceive in the skeletons of these three families, a very 

 close affinity; though each has nevertheless its peculiar cha- 

 racters, which are as obvious as those apparent in the exter- 

 nal structure : the skeleton of the roller is in many respects 

 intermediate to those of the two others* In each, the ster- 

 num has four unossified posterior emarginations, the outer of 

 which extend almost half way up the bone, and nearly twice 

 as far as the inner: in the bee-eaters, the thin slip of bone 

 which separates these emarginations, is inclined inward, con- 

 verging toward the medial plane; a structure which is farther 

 carried out in the jacamars : in the rollers it is less noticeable; 

 and not in the kingfishers, old specimens of which have some- 

 times the outer notch reduced to a foramen, by the gradual 

 deposition of bone : the keel is well developed; its anterior 

 angle being sharp in the halcyons and kingfishers, less so in 

 the rollers, and comparatively obtuse in the bee-eaters ; in 

 which last, however, the projection is continued farthest for- 

 ward : the coracoids are shortest in the bee-eaters, and most 

 elongated in the kingfishers ; and the furcula is broad and 

 thin, forming a wide arch, which, in the rollers, is rather more 

 lengthened than in the others, and exhibits a slight enlarge- 

 ment at the junction of the clavicles of which it is composed, 

 but no regular appendage analogous to the vertical one ob- 

 servable in all the Cantrices : the bee-eaters have a rib less 

 than the others. The sternal apparatus of the genera Nycti- 

 ornis and Eurystomus remain J;o be described; but probably 



* A skeleton of the European bee-eater is in Mr. Yarrell's valuable col- 

 lection ; and those of two species of roller in the museum of the Royal Col- 

 lege of Surgeons. 



