410 CHARLES CLIFFORD MACKLIN 



The medial surface of the ectethmoid is comphcated, but is, 

 in a general way, concave. Dorsally may be seen (f gs. 12 and 

 14) the processus cupularis posterior projecting forward freely 

 into the mesenchyme. This is the last remnant of the lamina 

 transversahs posterior which is found in the rabbit (Voit), 

 in which animal it connects ventrally with the paraseptal car- 

 tilage, but in my model there is no such connection. This is 

 the only part of the dorsal border which turns inward, and is 

 thus the sole representative of the median part of the cupola 

 posterior, described for many of the lower forms. A portion of 

 the dorsal border, a little below the lower margin of the bridge 

 of cartilage which joins the tectum nasi to the septum is partially 

 cut off by a thin sheet of perichondrium, and it also presents 

 a slight thickening. Its cartilage at the ventro-cranial edge is 

 slightly younger than that found in the adjacent wall. This may 

 be the homologue of one of the ethmoidal conchae of the lower 

 forms (fig. 12). Below the dorsal portion of the tectum is to be 

 seen a small fossa, probably the representative of the spheno- 

 ethmoidal recess of the adult condition, and this is bounded 

 below by the anlage of the superior nasal concha (fig. 16). The 

 latter is a small ridge of cartilage which stretches across from the 

 medial surface of the planum antorbitale behind to the attach- 

 ment of the middle concha with the wall, in front. 



Below and behind the superior concha is to be seen the superior 

 meatus of the nose (fig. 12), and it may be noted that this narrows 

 below by reason of the fact that the line of attachment of the 

 middle concha, which forms its lower and anterior boundary, 

 runs from above downward, as well as backward. 



The middle nasal concha (figs. 12 and 16) is somewhat larger 

 than the superior, and presents an irregular lower edge which 

 may be followed from a swelling of the lateral wall (which cor- 

 responds to the antero-lateral sulcus of the outer surface) back- 

 ward and downward to tenninate at the apex of the ventral 

 palatine notch by running over upon the dorsal edge of the infe- 

 rior concha. The edge of the middle concha is composed of very 

 young cartilage. The middle concha is perforated, near its 

 upper end, by a small foramen, filled by connective tissue. Its 



