036 J. PLAYFAIR MCMURRIOH. 



ment shows the metapterygoid at this stage to be an entirely 

 difFereut cartilage, and since, by repeated observations, I have 

 satisfied myself of the absence at this point of a chondrificatiou 

 distinct from the hyomandibular, and of the existence of au 

 elliptical foramen, which, being covered by a band of muscular 

 tissue, might easily be mistaken for a line of separation, I take 

 exception to Ryder^s identification. 



Having thus started on the wrong path, the homologies con- 

 tinue to be erroneous. Thus the distal horizontal portion of 

 the hyomandibular arch is termed the quadrate, whereas, from 

 its relations and from the evident absence of articulation between 

 it and Meckel's cartilage, it must be the symplectic. 



But it is in the homologies of the two upper cartilages of the 

 arch that Dr. Ryder errs chiefly. He says : " Above the articu- 

 lation of the quadrate (i. e. the symplectic of my figures) with 

 Meckel's cartilage a curious bent element (x) appears to repre- 

 sent the superior maxillary. Just in front of the expanded 

 upper extremity of the maxillary lies the posterior extremity 

 of the upper labial or intermaxillary element (la), which is 

 continuous with a similar piece on the opposite side ; this in- 

 termaxillary bar curves over the anterior upward bend of the 

 rostral cartilage (r. c). It contributes the skeletal boundary 

 of the upper part of the oral opening (m'), and is not seg- 

 mented in the median line, so as to articulate with its fellow 

 of the opposite side, like Meckel's cartilage of the lower jaw." 

 Now, in the first place, I differ from him in regard to his 

 assertion that the intermaxillary bar, as he calls it, curves 

 over the rostral cartilage. In Syngnathus these bars, as seen 

 from a surface view (fig. 4), certainly articulate with the sides 

 of the rostral cartilage, though when viewed from the side the 

 turned-up extremity of the latter gives at first sight an im- 

 pression of their continuity across the front of the skull. In 

 the second place I differ as to the identification of the car- 

 tilages. The terms "maxillary" and "intermaxillary" are 

 misnomers, the bones so denominated in the adult being, 

 without exception, membrane bones ; and further, the develop- 

 ment of the lower cartilage, and the fact that it is the only 



