300 34 



tured, a longitudinal ridge, beginning from about the posterior angle, and continued 

 by the above-described ridge on the quadrate, separates the cheek face proper from 

 the inwards sloping under face. 



The typical three opercular bones are present; but the suboperculum (s) is 

 concealed by the operculum (o) (PI. V, fig. 5), and the interoperculum (io) is gener- 

 ally only to be seen from below. 



The operculum is large, vaulted, its upper anterior angle, outside the articula- 

 tion with the hyomandibular, is drawn out into a muscle-process; the concave 

 inner face shows a strong muscle-ridge, starting from the lower margin of the arti- 

 cular fossa. The suboperculum is extremely thin, sickle-shaped, hidden by the 

 lower part of the operculum, only its hinder end is sometimes seen projecting out- 

 side the operculum into the opercular membrane; the latter besides encloses the 

 two long and slender branchioslegal rays (r). Interoperculum (io) thin, fairly high, 

 pointed at botli ends, the front end joined by the ligament (li) to the angular, the 

 hind end by the ligament (li') to the hyoid (to the process of the latter below which 

 the branchiostegal rays are attached). 



The infraorbitals are represented by the two large bones ao and ao' (PI. V, 

 figs. 4, 5), which however do not contain any lateral-line canal. The posterior (ao) is 

 situated in the normal position for the antorbital (or preorbital); it is bound by 

 strong connective tissue to the prefrontal, and in front of this spot it is emar- 

 ginated for the nasal opening; inside the connection with the prefrontal the 

 upper margin is firmly joined to the upper branch of the symplectic; the lower 

 margin is suturally connected with the preoperculum, the front margin with the 

 anterior preorbital (ao'). The latter is more elongated, its upper margin joined to 

 the upper branch of the symplectic and to the entopterygoid, the lower margin 

 to the outside of the quadrate; the front margin is free. The convex outer face 

 of both antorbitals is sculptured; between their inner concave face and the outer 

 face of the true suspensory bones is the Muse, adductor mandihulæ, the tendons of 

 which appear below the margin of the foremost preorbital, branching to the 

 mouth parts. 



It is a curious fact that some of the previous authors did not recognise these 

 bones as infraorbitals in spite of their position outside the muscles, covering these. 

 That some authors have regarded the anterior infraorbital as the metapterygoid 

 might be excused by the circumstance that its upper margin is suturally connected 

 both to the entopterygoid and to the symplectic and thus to a certain degree plays 

 the part of a metapterygoid; but in some other Syngnathids (e. g. Nerophis) it does 

 not enter between the suspensorial bones, and besides its relation to the muscu- 

 lature ought to have prevented the mistake. That the posterior bone must be 

 homologous to the preorbital, I think nobody will question; but in teleosts gener- 

 ally no bones are found in front of the preorbital; nevertheless they may occur in 

 some fishes, as I have shown to be the case in Amphisile, where 1 — 4 small bones 

 appear in this position. That no canal for the lateral line is present in the infra- 



