

— 152 — 



The SUPRAPREOPERCULAR is in contact, by its ventral edge, with thc dorsal end of 

 the preopercular, and is partly traversed by, and in part forms a bounding wall of the dorsal end 

 of the preopercular latero-sensory canal; but it lodges no organ of that canal. Its dorsal end lies 

 immediately behind the posterior articular head of the hyomandibular, and this end of the supra- 

 preopercular is firmly attached to a flange of bone that fills the obtuse angle between the posterior 

 articular head of the hyomandibular and its opercular articular head, a circular passage being left 

 between the twobones to transmit the dorsal end of the preopercular canal. The coinciding dorsal edges 

 of the suprapreopercular, and the flange of the hyomandibular to which it is attached, form a broad 

 surface which is slightly concave, is marked with transverse Striae, und articulates with the lateral 

 edge of the pterotic. The articulation is, accordingly, in part with a dermal bone, probably of latero- 

 sensory origin, and in part with a portion of the hyomandibular that is apparently of membrane 

 origin. This latter articulation, with a portion of the hyomandibular that is apparently of membrane 

 origin, is found alone, but much more developed, in Dactylopterus. The intimate attachment of 

 the suprapreopercular to the hyomandibular has not only completely blocked the passage for the 

 dilatator operculi muscle, but has cut that muscle into anterior and posterior portions, as already 

 described. 



The anterior and posterior articular heads of the hyomandibular lie close together, on the 

 dorsal end of the bone, separated by a narrow roughened surface that has the appearance of dermal 

 bone. The opercular articular head is long and slender, and is connected, by a wide web of bone, 

 with the ventral portion of the shank. The bone is traversed by the canal for the hyoideo-mandibularis 

 facialis, a single small branch canal transmitting a nerve destined to innervate, as in the other fishes 

 described, certain organs in the preopercular. 



The SYMPLECTIC is a slender bone, with a flattened distal end which lies in the symplectic 

 groove on the inner surface of the quadrate. Between this flattened distal portion and the proximal 

 end of the bone, the symplectic arches slightly, leaving a long but narrow space between itself and 

 the preopercular, this space transmitting the ramus mandibularis externus facialis and the arteria 

 hyoidea. The mandibularis internus facialis passes anterior to the symplectic, between that bone 

 and the hind edge of the quadrate, as in the other fishes of the group. 



The hyomandibulo-symplectic interspace of cartilage lies in the little concave surface in the 

 angle between the dorsal and ventral limbs of the flange on the inner surface of the preopercular, 

 as already stated, but it occupies only the dorsal portion of the concavity. Ventral to it, the 

 remainder of the concavity lodges the small interhyal, that element articulating with the cartilage 

 in a little facet on its ventro-posterior surface. In the corner between the cartilage, the inner surface 

 of the preopercular, and the ventro-posterior corner of the hyomandibular, there is a small opening 

 which transmits the ramus hyoideus facialis. 



The QUADRATE has a well developed posterior process, and on the lateral surface of the 

 postero-ventral edge of this process there is a wide, flat flange. This flange projects dorso-laterally 

 at an acute angle to the flat, plate-like body of the bone, and its anterior end is prolonged forward 

 beyond the anterior edge of the body of the bone as a strong anterior process. The ventro-posterior 

 surface of the body of the flange fits, in larger part, against the internal surface of the ventro-anterior 

 end of the preopercular, in the angular groove between the body of the bone and the ventral limb 

 of the flange on its internal surface; but a small anterior portion of this surface fits against the internal 



