— 16 — 



of the arm of the bone. The space enclosed in this rounded angle is further bounded, latero-anteriorly, 

 by the dorsal edges of the lachrymal and palatine, a large oval or rounded passage thus here bein«? 

 formed, between these several bones, which leads from the dorsal to the ventral surface of the skull 

 immediately lateral to the nasal region. 



On the dorsal surface of the skull, the mesial edge of the superficial, dermo-perichondrial portion 

 of the body of the ectethmoid is serrated and articulates, by suture, with the corresponding portion 

 of the mesethmoid, the two bones forming the floor and mesial wall of the nasal pit. On the ventral 

 surface of the skull the body of the ectethmoid everywhere lies directly upon or is in synchondrosis 

 with the antorbital cartilage, and is there overlapped externally, along its mesial edge, by the lateral 

 edge of the parasphenoid. Anteriorly, on the dorsal surface of the skull, an interspace of cartilage 

 separates the body of the ectethmoid from the dorsal limb of the voraer, this interspace being bounded 

 mesially by the mesethmoid. On the ventral surface of the skull, in small and even medium-sized 

 specimens, this same interspace of cartilage intervenes between the anterior portion of the body of 

 the ectethmoid and the postero-laterally presented lateral edge of the body of the vomer; but in large 

 specimens, the interspace may be cut into two portions by the backward growth of a process of the 

 vomer, this process meeting or even overlapping externally the anterior edge of the ectethmoid. The 

 lateral edge of the interspace turns slightly upward, and may present an angle, which then forms a 

 prominence on the lateral edge of this part of the skull. The lateral portion of the ventral surface 

 of the interspace, the part that lies lateral to the process of the vomer, when that process exists, is 

 presented ventrally and slightly latero-posteriorly, and gives articulation to a small articular surface 

 at the base of the maxillary process of the palatine. In Scomber, I described this articular surface 

 of the ethmoid cartilage as the ventro -lateral, or septo maxillary process of the mesethmoid, it being 

 the mesethmoid instead of the ectethmoid that, in Scomber, forms its principal support. In most 

 current descriptions of the teleostean skull, it is called the anterior palatine, or prepalatine articular 

 surface or process, the articular surface on the outer end of the ventral process-like portion of the 

 arm of the ectethmoid being called the posterior palatine or postpalatine articular surface or process. 



The posterior surface of the ectethmoid forms the concave anterior wall of the orbit; the wing, the 

 arm, and the body of the bone all contributing to it. At the anterior end of the orbit, and somewhat 

 above its floor, there is a pit-like depression, lying partlvin the bodyof the ectethmoid and partly in 

 the adjoining cartilage. The pit gives insertion tothe oblique muscles of the eye, and is accordingly the 

 anterior eye-muscle canal. In it, close to its lateral edge, is the posterior opening of the olfactory 

 canal through the antorbital process, that canal being entirely enclosed in the body of the ectethmoid. 

 Immediately lateral to the pit, a strong ligament has its origin, as in Scomber, and running downward 

 is inserted on a transverse ridge-like process of the palatine cartilage that forms the hind edge of the 

 posterior ethmoid articular surface of that element. This ligament is thickened at either edge, thus 

 seeming to represent two ligaments incompletely fused with each other. 



Ridewood says ('04a, p. 56) that the ectethmoid (his prefrontal) is usually formed by the fusion 

 of originally separate ectosteal and endosteal components, and he says (1. c, p. 39) that the bone is 

 „purely ectosteal" in Elops. As, in my work, I have never found a dermal ectethmoid, I have exa- 

 mined Elops carefully in this connection, and the bone, in my specimens, is certainly similar to the 

 bone of Scorpaena: that is, it is formed of a perichondrial layer that has acquired dermal accretions, 

 and these accretions do not represent a separate dermal component that has fused with an underlying 

 perichondrial one. That an independent and purely dermal ectethmoid, related to an underlying 



