PROFESSOR OWEN ON THE GENUS DINORNIS. 349 



prelacerate (/) foramina, beneath which there is thus a smooth depression (lo) capable 

 of receiving the end of a man's thumb on each side and above the origin of the 

 presphenoid. In advance of these depressions the outer plates of the neurapophyses 

 (PI. LVI. fig. 1, u) extend obliquely outward as they rise, forming the sides of the 

 larger rhinal chamber (PI. LIV. fig. 1, n), and passing uninterruptedly to coalesce 

 with the superorbital expansions of the frontal (neural spine, PI. LIII. fig. 1, ii). 

 From the upper and anterior half of the presphenoid rostrum, the inner plates of 

 the neurapophyses (h) — foremost terminal ones of the series — converge and coalesce 

 into a vertical wall of bone (PI. LVI. fig. 3, i4'), thickest, lengthwise, at its middle 

 part and thence gradually thinning off to both posterior and anterior margins, but 

 thinnest vertically at its middle part, and expanding both below and above. Superiorly 

 the expansion attains a breadth of 8 lines, with a flattened upper surface (ib. fig. 3, w ) 

 supporting the fore part of the nasals (is), which part is overlapped by the premax- 

 illary, and with the under surface forming an arch on each side over the fore part of 

 the rhinal chamber. 



The base of each of these neurapophysial plates, prior to their rising to converge 

 and coalesce, developes a strong, thick, dense, and smooth girdle of bone around 

 the orifice of communication between the rhinal chamber and the corresponding 

 nasal passage: the girdle (ib. fig. 1, g, g', g") is not entire; about one-sixth is incom- 

 plete at its fore part ; the orifice it otherwise would encompass is of a triangular 

 form, with the angles rounded off (ib. 19). The hinder side or bar (g) is transverse 

 to the skull's axis, and is 1 inch long ; the medial side (g') is in the skull's axis, 

 and is 10 lines long; the third side, partly formed by the bending of the outer 

 end of the hind bar, extends obliquely forward and inward for 6 lines, leaving about 

 the same extent of the circumference incomplete at its middle, between the above and 

 the process (ib. g"), which extends transversely outward. The inner part of this thick 

 border or girdle is defined from the base of the neurapophysis developing it by a narrow 

 groove ; the hind part increases in depth as it extends outward and makes a bold bend 

 forward and inward, with the convexity projecting into the fore part of the orbit, as 

 it bends to form the anterior part of the girdle. There is a small perforation at the 

 convex bend, and the upward continuation of this part of the wall, which is concave 

 forward, becomes as thin as fine paper, subreticulate, and continuous with the delicate 

 bony support of a turbinal (ib. 19). We have here the commencement of the accessory 

 or apophysial part of the neurapophysis, which becomes developed into the most con- 

 spicuous part of the 'frontal anterieur' of Cuvier, e.g. in Reptiles. But in Dinornis 

 the ' prefrontals ' are unwontedly developed in their essential parts, and almost exclu- 

 sively devoted to the olfactory chamber, which is serially homologous with the orbit 

 and the tympanum, as the antecedent nasal passage conducting the air thereto is the 

 homotype of the meatus auditorius externus in the hinder organ of special sense. 



On removing the centrum and lower portions of the neurapophyses of this region of 



