Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 50 



Sagemehl as a lateral process of the vomer and said by him to be 

 partly ossified, in certain species, as the septomaxillary (No. 66, 

 p. 510). 



Posterior to its lateral processes, between them and the hind 

 end of the bone, the ethmoid is constricted laterally, the constric- 

 tion being most pronounced slightly below the dorsal surface of 

 the bone. This part of the bone forms the anterior part of the 

 mesial wall of the nasal pit, and a part of the floor of that pit. 

 It is separated, posteriorly, from the preorbital ossification, by 

 a narrow line of cartilage, but this cartilage may be bridged, near 

 the middle of its length, by an exceedingly thin but wide splint- 

 like process of the ethmoid. Ventrally the ethmoid may touch, 

 or be slightly overlapped by, the dorso-lateral edge of the vomer. 

 In front of its lateral process the bone is somewhat rounded, and 

 has a median ridge-like portion which is continuous, anteriorly, 

 with the beak of the chondrocranium, its dorsal surface running 

 forward and downward in a slightly curved line. Directly on 

 top of this portion of the bone, and immediately postero-dorsal 

 to the rostrale, there is, in the recent state, a tough pad of tissue, 

 which is strongly but loosely attached to the top and sides of the 

 ethmoid and hence capable of considerable movement. 



In the interior of the ethmoid there is always a median space, 

 of variable size and shape, filled with a semi-liquid, fatty or oily 

 substance. In one specimen this space was almond-shaped in both 

 horizontal and vertical sections, its hind end coming to the hind 

 edge of the bone, and its front end reaching to abotit the anterior 

 third or quarter of the bone. In another specimen it was oval 

 and small in vertical section, instead of being almond-shaped and 

 large, and lay at about the dorsal third of the bone. In a third 

 specimen it was round, or sub-cubical, occupied the whole posterior 

 third of the bone, excepting only thin dorsal and lateral plates, 

 and, ventral to the inferior surface of the bone, extended slightly 

 into the underlying cartilage. It is the mesoethmoidal fat-cavity 

 described by Parker (No. 50, p. 108) in Sahno, and considered 

 by him, in that fish, as a "remnant of the azygous nasal sac of the 

 Myxinoid." 



The ethmoid of Scomber is thus seen to be in no part or way 

 the homolosrue of the so-called ethmoid of Ainia. This has 



