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by the hiiicl end of a narrow and low median ridgc of cartilage which represents tlie relatively tall 

 internasal ridge of Scorpaena. On either side of this ridge the mesethmoid is bounded by the hind 

 edge of the corresponding ascending process of the vomer. 



The mesethmoid is bounded, on either side, in its posterior half or two-thirds, by the ecteth- 

 moid, the hind end of the mesethmoid iisually projecting beyond the bounding poitions of the ecteth- 

 moids and there suturating with or being overlapped externally by the frontals. The anterior half 

 or third of the bone gives support, on either side, to the nasal, the mesial half of the latter bone over- 

 lapping and lying upon a depressed lateral half of the dorsal surface of this part of the mesethmoid. 

 The antero-lateral corner of the dorsal surface of the mesethmoid projects forward as a sharp pro- 

 cess, and from this process and from the ventral surface of the overlying nasal, the ethmo-maxillary 

 ligament has its origin. This little corner or process of the mesethmoid, together with the adjacent 

 parts of the flat dorsal surface of the bone, thus replace functionally, in their relations to the nasal 

 bone and the ethmo-maxillary ligament, the pronounced mesethmoid process of the Scorpaenidae. 



The lateral edge of the mesethmoid, beneath the nasal, is grooved and forms the median wall 

 and part of the floor of the shallow nasal pit. Posterior to the nasal, this same grooved edge of the 

 mesethmoid forms the mesial wall of the olfactory canal through the antorbital process. Dorsal to 

 this groove, between it and the thin dense external plate of the bone, there is another groove in the 

 lateral edge of the bone, this groove lying between the suturating edges of the mesethmoid and 

 ectethmoid. A canal is thus here formed between the two ethmoid bones, which, in large specimens, 

 may become entirely enclosed in the mesethmoid alone, continuing posteriorly to the hind edge of 

 that bone. It lodges that part of the supraorbital latero-sensory canal that lies between the frontal 

 and nasal bones, but contains no sensory organ, the sensory canal thus here being secondarily and 

 not primarily enclosed in the bone. 



Under the central portion of the bone, primary ossification has begun, and, in large specimens, 

 extends entirely through the cartilage of the snout. In the central portion of this part of the bone, 

 in three specimens that were bisected, there was a large cavity filled with fatty tissue. 



The ECTETHMOID has a convex dorsal surface, this convexity being so great in the posterior 

 portion of the bone that a transverse section here has the shape of a quadrant of a circle. The external 

 surface of the bone lies, as already stated, on a level with the corresponding surface of the other bones 

 of the dorsal surface of the skull, and is marked by radiating and granulated ridges. The hind edge 

 of the bone is thin and sharp, and projects posteriorly to form the anterior portion of the roof of 

 the orbit. It bears the two or three preocular spines, the postero-mesial one of these spines being 

 considerably longer than the others. The mesial edge of the bone suturates, in its posterior portion, 

 with the frontal, and, in its anterior portion, with the mesethmoid and the hind end of the nasal. 

 Along the mesial edge of the posterior portion of the bone, beneath the overlying frontal, there is 

 a small canal which transmits the ramus ophthalmicus superficialis, this canal leading from the orbit 

 into that larger canal, already described, that lies between the mesethmoid and ectethmoid and that 

 lodges the supraorbital latero-sensory canal. 



The ventral surface of the ectethmoid is large and inclines downward and mesially at an angle 

 approximately of 30 " with a horizontal plane. Along the lateral edge of this surface there is a stout 

 and irregulär longitudinal ridge which projects downward and but slightly laterally. The anterior 

 half of this ridge has a somewhat rounded summit, and this part of the ridge gives articulation to 



