The Lateral Sensory System in the Muraenidae. ]^37 



membrane that lies directly upon tlie dorsal surface of the skull, the 

 fibres of the adductor muscle run downward and forward, about one 

 half of them passing" anterior to the postorbital process of the skull and 

 the other half posterior to that process, the process itself and the 

 entire dorso-lateral edge of this part of the skull thus being- buried 

 beneath a thick layer of this muscle. A considerable part of the 

 muscle also arises from the anterior surface of the postorbital process 

 and from the lateral surface of the skull immediately anterior to the 

 process. The eye-ball is thus pushed relatively far forward, the post- 

 orbita] process lying' about midway between the orbit and the hind 

 end of the skull. All this is, I suppose, well known, but I do not 

 find it mentioned in any of the works at my disposal. It is here so 

 especially referred to because of the effect that this unusual develop- 

 ment of the muscle, and the concomitant displacement of the orbit, 

 has had upon certain parts of the lateral sensory system. Muraena 

 differs from the other Muraenidae examined in that the two aponeu- 

 roses that give origin to the supracranial extension of the adductor 

 muscle are but slightly, or not at all developed, and that the trunk 

 muscles push forward a short distance superficial to the hind end of 

 the adductor. Between the two overlapping muscles, in the loose con- 

 nective tissues that separate them, the supratemporal ossicles lie, 

 without definite attachment to the skull. The course of certain of 

 the nerves, to be later given, show definitely that the supracranial 

 extension of the adductor muscle of these several fishes is a secondary 

 acquisition, the muscle having pushed upward and backward from the 

 cheek on to the dorsal surface of the skull. 



The anterior nasal aperture of Conger (figs. 13 — 21) lies on the 

 summit of a short tube, which rises from the lateral edge of the 

 anterior part of the snout a short distance only above the ventral 

 edge of the upper lip. It is directed downward, forward, and laterally, 

 its lower end projecting slightly below the ventral edge of the upper 

 lip. The posterior aperture is a fairly large pit lying anterior to and 

 not far from the eye, slightly dorsal to its mid-horizontal plane. The 

 nasal sac is a tubular structure extending between these two aper- 

 tures, immediately internal to the nasal bone. 



