PEOFESSOE OWEN ON THE GENTJS DINOENIS. 125 



rest of the pelvic disk (PI. XV. fig. l,r,r) is bounded externally by the strongly pro- 

 duced ridge overhanging the vertical postacetabular plate (PI. XIV. fig. 1, 62, I) of the 

 ilium, which coalesces with the similarly vertical expanding plate of the ischium (ib. 63). 

 The foramen (ib. m) between the ilium and beginning of the ischium is a full ellipse or 

 oval. The ischium developes downward a ridge, behind the obturator notch (q) ; but 

 this does not meet the ridge reciprocally directed upward from the pubis (ib. 64) : there 

 are impressions of the attachment of a strong fibrous sheet which closed the obturator 

 groove behind ; and this sheet becomes a thin plate of bone in old individuals of some 

 existing Eallines {Tribonyx ventralis, Ocydromus australis). 



The proportions and form of so much of the pubis (64) as is preserved adhere to the 

 ralline type of that bone ; but the tubercle, prominent below the fore part of the bone 

 in most existing Rallines, is not developed in A^dornis. 



I have restored, in dotted outline, the parts of the ischium and pubis broken away 

 from the otherwise complete and truly singular and interesting form of pelvis in 

 Aptornis defossor. It may aid in future comparisons of this most complex of bones to 

 subjoin a list of the parts of the pelvis, conveniently indicated by names, with the 

 symbols used to indicate them in PI. XIV. fig. 1, and PI. XV. 



The specimens of Aptornis defossor above described are from a cavernous fissure at 

 Timaru, Canterbury Settlement, South Island of New Zealand. I am indebted to 

 Dr. D. S. Price, of the Crystal Palace, Sydenham, for the much valued opportunity 

 of describing, comparing, and figuring them. 



Parts of the Pelvis of Aptomis defossor, Ow. 



a. Acetabulum (the letter marks, in PI. XIV. fig. 1, the inner aperture). 



b. Postacetabular facet. 



c. Centrum (marking, in PI. XV. fig. 2, the ridged underparts of the first and second 



sacral vertebree). 



d. Centrum (marking the unridged underparts of succeeding centrums). 



d. Diapophysis (marking, in PI. XIV. fig. 1, the diapophysial articular surface). 



e. Subacetabular fossa. f,f. Antacetabular part of ilium (PI. XV. fig. 1). 

 g. Gluteal ridge. /*. Gluteal process (PI. XIV. fig. 1). 



i. Ilium (marking, in PL XV. fig. 2, the part anchylosed with and overhanging the 



foremost diapophysis). 

 id. Interdiapophysial vacuities (marking the six anterior ones). 

 I. Postiliac tuberosity. m. Ischiadic foramen. 



n. Neurapophysis ; w' in PI. XV. fig. 1, is the fore part, n* the hind part, of the neur- 



apophysial crest. o. Ilio-neural orifices. 



p. Parapophyses, | both combine to separate, below, the interdiapophysial vacuities : 

 pi. Pleurapophyses,/ in PI. XIV. fig. l,pl marks the articular surface for the head 



of the first sacral rib. 



