418 Mr. II. Seebohm on the 



with the adjoining vertebrse in the different modes already 

 described. At the bottom of the centrum, that is to say 

 opposite the neural spine, a ventral process (the hypapo- 

 physis) frequently occurs. 



The number of rib-bearing vertebrse which are unfurnished 

 with ventral processes vary very much in the group of birds 

 under consideration. It is greatest in the Rallidse and 

 Gruidse (6 to 7) and in Thinocorus (7). In the LaridjB and J 

 Charadriidse the usual number is 5 (as it is also in the Oti- ^ 

 didse), but in some of the Alcidse it is only 2. In the 

 Cracidse it varies from 3 to 4, as it does also in the Turni- 

 cidse and the Pteroclidrc. It is smallest in the Gallinjc, the 

 Impennes, the Crypturi, and the Colymbidae, and in most 

 of the Tubinares (0 to 2) . In the last-mentioned suborder 

 the number is 4 in Oceanites and Diomedea. 



Media)! Processes of the Furculum. 

 At the junction of the two halves of the furculum (or 

 merrythought) a median process (the hypocleidium or inter- 

 clavicle) is frequently developed. In the remarkable bird 

 Opisthocomus it forms a long bone uniting the furculum with 

 the sternum. In the Cracidse it is much prolonged, and it 

 is Avell developed and usually laterally flattened in all the 

 Gallinie. In all the other suborders under consideration it 

 is either very small or absent. 



Pneumaticity of the Humerus. 

 I am inclined to agree, to a certain extent, with Professor 

 Huxley in his assertion (Proc. Zool. Soc. 1868, p. 296) that 

 the pneumaticity or otherwise of certain bones of birds is a 

 character of no systematic value, though the isolated case to 

 which he refers is not a case in point. Prof. Parker has 

 since discovered that the statement that the Cracidse differ 

 from the Megapodidse in this respect was an error. No 

 osteological character appears to be constant in every group, 

 aiul I do not know that the character in question is much 

 more erratic than others which are admitted to be of some 

 taxonomic importance. 



