1868.] Prof. Huxley on Arcliseopteryx litliographica. 245 



A full description of this mass of bone as *^ the left os innominatum, in- 

 cluding the anterior two-thirds of the ilium, and the anterior half, or more, 

 of the coalesced ischium," is given at p. 39 ; and at p. 40 I find, " The 

 inferior or central* face [of the sacrum], as in the case of the slightly dis- 

 located left innominatum, is towards the observer." 



There is no doubt on any side, that the end of the bone in question which 

 at present is directed forwards is its true anterior end, and that the edge 

 which is turned towards the spinal column is the true dorsal edge. The 

 question is, whether the face of the bone which is exposed is its outer (or 

 dorsal) or its inner (or ventral) face. In the former case it must needs be 

 a right ilium, in the latter a left ilium. 



That it is the outer face of the bone which lies uppermost appears to me 

 to be demonstrated — 



(a) By the fact that the iliac margin of the acetabulum is prominent, 

 and that the adjacent surface of this ilium rises to this margin. I am not 

 aware that any vertebrate animal exists in which the acetabulum lies at 

 the bottom of a funnel-shaped depression, such as would be the case in 

 Archceopteryx if the bone in dispute were the left os innominatum seen 

 from the inner side. 



{b) By the fact that a small portion of what appears to be an innominate 

 bone can be descried in close relation' with the proximal end of what has 

 just been shown to be the left femur ; while the right femur (called 

 left in the memoir), though dislocated, is not very far from the bone under 

 discussion. 



(c) By the further consideration, that if this were not the right os in- 

 nominatum, it would be as curiously unlike the corresponding bone of a 

 bird in the form of its surface as it resembles it in all other respects. 



4. The bone marked 51' is named "left scapula" (I. c. p. 34), and 

 that marked 51 *' right scapula " (I. c. p. 35) ; and a full description of 

 these bones, as such, is given at pp. 36 and 37 of the memoir cited. 



Nevertheless I venture to affirm that 51' is the right scapula and not the 

 left ; for it will not be denied that the anterior or glenoidal end of the bone, 

 as it now lies, is directed forwards, its posterior or vertebral end backwards, 

 and its glenoidal articular surface outwards and forwards : it would be quite 

 impossible to put a left scapula of similar construction into this position. 



Further, the glenoidal end of this scapula remains in connexion with 

 what is obviously the glenoidal (or humeral) end of the right coracoid 

 (marked c in Plate I.). The author of the memoir, indeed, gives a different 

 interpretation of the osseous projection thus marked (I. c. p. 37) : — 



"The prominence beyond the left scapula (Plate I. 51') suggested at 

 first view the humeral end of the coracoid, but I believe it to be part of the 

 humerus corresponding with the tuberosity on the ulnar side of the sessile 

 semioval head, overarching the pneumatic foramen in the bird." 



* " Central " in the original. The word appears to have been substituted by an 

 error of the press for " ventral." 



VOL. XVI. Z 



