* of the Fishery Board for Scotland. 



285 



attached to the upper posterior corner of the interoperculuni. Its upper 

 anterior edge is overlapped by the lower edge of the oblong operculum 

 (oper.). The upper corner of the latter is rounded, while its lower corners 

 are somewhat sharp, the lower border forming a slightly curved descending 

 line. Near its upper end, and on its anterior edge it is thickened to 

 form a cup-shaped cavity for articulation with the hyomandibular. All 

 the opercular bones are thin striated laminae, bearing a close resemblance 

 in structure to the scales. 



Articulating with the ventral margin of the hyomandibular and 

 symplectic at their junction, is a short rod-shaped interhyal (PI. XV. 

 fig. 1, i.hy.), the ventral end of which is connected with the posterior 

 upper corner of the epihyal. The epihyal (ep.hy.) has its posterior end 

 somewhat pointedly rounded, with a small articular surface on its upper 

 posterior corner for the interhyal. It has attached loosely to its outer 

 lower surface the three posterior branchiostegal rays. Its anterior edge 

 is connected with the longer flat ceratohyal, which has its lower edge 

 curved upwards or emarginated. Near its edge the ceratohyal is per- 

 forated by four or five small foramina, through which pass the proximal 

 sharp ends of the five anterior branchiostegal rays. The bone completing 

 the lower edge of these perforations is sometimes very slight, or even 

 wanting, so that the rays may appear to pass directly to the inner side of 

 the ceratohyal. 



The eight branchiostegal rays become slightly shorter the one than the 

 other from before backwards. The posterior (outer) three (brs.r.) are 

 simple flat bones. The posterior widest, and with a straight anterior edge, 

 and curved posteriorly, is slightly wider at its distal than its proximal 

 extremity. The penultimate ray is narrower, and nearly the same width 

 throughout. That anterior to it terminates in a sharp point. These have 

 all more or less of a short process from their upper ends, by which they 

 more particularly are attached to the epihyal. The five anterior rays are 

 more rod-like and slender, and in place of overlapping each other like the 

 posterior three, they lie apart, simply connected by the intervening mem- 

 brane. At the anterior end each ceratohyal is terminated by a pair of 

 thick short hypohyals, over and projecting in front of which is the 

 lozenze-shaped cartilaginous tongue, bearing on its upper median sur- 

 face a narrow oval thin bony scale, provided with a double series of small 

 teeth ; while posteriorly there projects backwards in the ventral middle 

 line the long flat urohyal bone, widest posteriorly, with a rounded end, and 

 articulating anteriorly by a small nodular head. . 



From the cartilaginous tongue extends backwards the short basi- 

 brauchial of the 1st gill arch. It has a ventral median ridge, and articu- 

 lates with the 1st hypobranchials on each side, the gill laminae which lie 

 in the postero-ventral groove of the latter running on to its sides. 

 From the basibranchial there pass up on each side the longer hypo- 

 branchials, succeeded by the still longer cerato-branchials, beyond which, 

 and forming an acute angle with them, are the epibranchials of similar 

 length to the hypobranchials; the latter gives off a short upstanding 

 process from its posterior margin near its tip, which is terminated by a 

 short small outstanding pharyngobranchial. The first three pieces are 

 grooved on their under surfaces, and the joint between each formed 

 by a small intervening cartilage. Behind, and separated from the 1st 

 basibranchial by a narrow cartilage comes the second, which is double the 

 length of the first, and hollowed underneath like the remainder of the 

 arch for the reception of the blood-vessels, gill filaments, &c. The second 

 hypo-, cerato- and epi-branchials are shorter than the first, and wider at their 

 distal (dorsal) ends, where, as before, a short process projects dorsally. The 



