20 



PROCEEDINGS OF THE NATIONAL MUSEUM 



In one respect, the lateralis system of Gadopsis is specialized con- 

 siderably less than that of the ophidioids. In Gadopsis, as in most 

 percoids, the ep axial body musculature extends forward over the 

 dorsal surface of the skull and attaches in part to a low supraoccipital 

 crest. The supratemporal commissure, as in most percoids and in 

 the gadoids, is incomplete; it extends upward on each side of the head 

 through the lateral extrascapular and then ends blindly over the 

 epaxial musculature noted above. In the other ophidioids, the epaxial 

 body musculature does not extend in over the skull; there is no supra- 

 occipital crest rising above the cranial surface; and the supratemporal 

 commissure is complete. There appears to be, as in the northern and 

 many tropical blennies, a medial (as well as a lateral) extrascapular 

 that has become fused completely with the parietal bones. 



me 



lo Po mo 



Figure 4. — Cranium of Gadopsis marmoratus (ab = attachment surface for Baudelot's 

 ligament, af= anterior facet for hyomandibular articulation, Ba = basioccipital, ca = 

 cartilage, Ep = epiotic, Ex=exoccipital, Fr = frontal, ho= hyomandibular opening of 

 trigemino-facialis chamber, In = intercalar, me = membrane, Me=mesethmoid, mo= 

 main opening of trigemino-facialis chamber, op = opening of supraorbital sensory canal, 

 Pa = parasphenoid, pf = posterior facet for hyomandibular articulation, Pi = parietal, 

 Pl = pleurosphenoid, Po=prootic, Pr=lateral ethmoid, Pt=pterotic, Sp = sphenotic, 

 Su = supraoccipital, Vo = vomer). 



In Gadopsis, as in other ophidioids, the eyes are relatively small or 

 completely absent. In all, the eyeball seems to be capable of slight 

 rotation or none. The eye muscles are weak and usually flabby in the 

 preserved specimens, and there are no eye muscle canals (myodomes) . 

 The eyeball is covered by a heavy membrane. In the ophidioids this 

 is taut over the eyeball, but in Gadopsis it appears to be infolded 

 around the eyeball, perhaps permitting greater eye rotation. 



The relatively small eye and weak eyeball musculature are contained 

 in a small eye socket. This I think is associated with certain features 

 of the skull in the interorbital region and of the brain and olfactory 



