FISHES OF FAMILY BLENNHDAE 29 



the lateral arm of the palatine lies internal to the concavity. The 

 third circumorbital is expanded mesially into a narrow subocular 

 shelf that overlaps the second and fourth circumorbitals. The dorsal 

 end of the fifth circumorbital attaches to the frontal. The fifth cir- 

 cumorbital is presumably the dermosphenotic. Each circumorbital 

 bears, or participates in forming, external openings to the infraorbital 

 sensory canal. The anterior termination of the infraorbital canal is 

 in the lachrymal, where the canal exits at three main openings: one 

 dorso-anteriorly and two lateroventrally. 



Sclerotic bones. — Each eye is bounded anteriorly and posteriorly 

 by a pair of separated, concave, sclerotic bones (not illustrated). 



Nasal bones (figs. 1, 3, 7). — The nasals are separated, elongate, 

 tubular bones with dorsal and ventral lateral projections. A latero- 

 sensory canal extends the length of each nasal and is continuous 

 dorsaUy with the supraorbital canal of the respective frontal. An 

 external opening in the head skin, just lateral to the anterior end 

 of each frontal, also leads to the nasal canal where the canal continues 

 from the nasal to the frontal. A second opening just below the dorsal 

 end of the nasal leads to an external opening adjacent to the posterior 

 nostril. The opening at the ventral end of each nasal exits externally 

 as a pore before each anterior nostril. The nasal capsule on each side 

 is between the two lateral nasal projections and is supported mesiaUy 

 by the broad flange that comprises the ventral projection. 



Opercular series (fig. 7). — The opercle is a thin, flat bone, except 

 for a thickened, anteriorly concave articulating surface at its dorso- 

 anterior end that articulates with the hyomandibular. Ventrally the 

 opercle inserts in a groove in the thin, flat subopercle. Dorso-anteriorly 

 the subopercle lies ventral to the opercle's posterior margin. A slender 

 extension of the dorsal end of the subopercle projects for a short 

 distance beyond the dorsal level of the opercle. The interopercle is a 

 short, bladelike bone that is well removed from the subopercle. The 

 interopercle is internal to the preopercle and is not visible when the 

 head is viewed laterally. The interopercle's anterior end is attached 

 by a ligament to the angular. The interopercle's posterior end is 

 thickened and ligamentously attached to the posterior end of the 

 epihyal, where the epihyal joins the interhyal. No portion of the inter- 

 opercle is posterior to the posterior end of the epihyal. Ligaments 

 also extend from the interopercle's posterior end to the subopercle's 

 ventral end. 



The preopercle is a crescent-shaped bone with a sensory canal 

 (preoperculomandibular) extending its entire length. The dorsal ex- 

 tension of the canal continues into an opening of the L-shaped lateral 

 extrascapular at the anterolateral angle of the lateral extrascapular. 

 The ventral extension of the canal enters the articular. There are 



