OSTEOLOGY, ETC., OF SYNGNATHUS PECKIANUS. 631 



a curved rod (H. M.), extending from the skull downwards and 

 forwards towards the proximal extremity of Meckel's cartilage* 

 with which it appears to articulate. Anteriorly it lies below, 

 and almost parallel to, the pterygo-quadrate cartilage, and 

 becomes somewhat broader posteriorly. It presents as yet no 

 differentiation into the hyomandibular and symplectic portions, 

 to which this segment of the arch corresponds, nor in fact does 

 it so separate afterwards, the line of division between the two 

 being indicated merely by the articulation of the second seg- 

 ment of the arch, i. e. hyoid portion. This consists at present 

 of a rod lying below, and inclined towards, the upper cartilage, 

 which it meets a little in front of the dilated portion. 



The remaining four arches constitute the branchial arches 

 (Brs.), present at this early stage to the same number as in 

 the adult. No azygos, median hyoid cartilage could be de- 

 tected at this stage, nor is there a median branchial cartilage. 



In Stage b (figs. 2 and 3) the mandible has become bent up 

 upon the skull, and the pterygo-quadrate cartilage retains the 

 same characters as in the preceding stage. The hyomandibular 

 has, however, undergone some modifications. It has become 

 distinctly angulated, the symplectic portion (Sym.) extending 

 forward parallel with the axis of the skull, while the hyoman- 

 dibular (H. M.) moiety is bent up almost at right angles to it, 

 slightly posterior to the eye, and articulates with the lateral 

 under-surface of the auditory capsule. Near the anterior 

 border of this portion is an oval foramen, and at the angle of 

 junction with the symplectic a separate cartilaginous centre 

 appears, uniting the hyoid to the hyomandibular portion of the 

 arch, and representing the interhyal. The hyoid arch (Hy.) 

 extends from this downwards towards the median line, and 

 represents the combined ceratohyals and hypoiiy als. About 

 halfway from the extremity of each portion of it is a process 

 extending upwards towards the symplectic, which is notched 

 to receive it. A median hyoid rod (G. H.) is now easily seen, 

 extending from in front of the hyoid cartilages back to the 

 branchial region. It is not quite straight, but curves slightly 

 to the side, and at the junction of the hyoid and hyomandibular 



