482 DR. AV, G. RIDEWOOD ON THE CRAXIAL [Dec. 13, 



contact with the front of the ceratohyal. The glossohyal is an 

 ill-defined cartilage of small size. The second basibranchial is 

 large in comparison with the first and third, but it is a hollow 

 shell of bone, the interior of which is occupied by a fatty mass. 

 The dentigerous membrane-bone that covers it overlaps the 

 posterior three-fourths of the first basibranchial and the anterior 

 third of the third basibranchial. 



The second hjqjobranchials are fused with the sides of the 

 second basibranchial, but the line of demarcation is obvious. The 

 thii'd hypobranchials are rather long, and slope forward and 

 downward at the sides of the third basibranchial. The urohyal 

 is long, and extends considerably behind the posterior end of the 

 third basibranchial. The epibranehials are longer than usual in 

 proportion to the ceratobranchials ; the fourth is moderately 

 expanded in a vertical direction. 



The first pharyngobranchial is cartilaginous ; and the spicular 

 bone pi'ojects upwai-d, backward, and outward, and is attached to 

 the pro-otic bone at the point marked s in text-fig. 136 B, p. 478. 

 The cartilaginous plate that i-epresents the fourth and fifth 

 basibranchials is continued back between the closely approximated 

 anterior ends of the fifth ceratobranchials, and projects some 

 distance behind as a free rod of cartilage. 



Changs salmoneus. 



The accessory branchial organ of Chanos, briefiy alluded to by 

 Johannes Mliller ('Ban und Grenzen der Ganoiden,' Berlin, 1846, 

 pp. 74 and 75), has beqn described and figured by HjTtl, but the 

 relations of the skeletal parts to this organ are not shown 

 (Denkschr. Akad. Wiss. Wien, xxi. 1863, p]3. 1-10 and pi. 1 ; 

 also Sitzungsber. Ak. Wiss. Wien, xliii. 1, 1861, pp. 155 & 156). 



Material examined. — In addition to two skulls (a large one, A, 

 and a small one, B) specially prepared for the purposes of this 

 investigation from alcohol-preserved specimens kindly furnished 

 by Mr. G. A. Boulenger, a third skull (C) was examined, belonging 

 to a skeleton in the Osteological Collection of the British Museum 

 (Brit. Mus. 98.9.13.1, Tongatabu). 



Crankmi (text-fig. 140, p. 483). — The cranium is broad and flat- 

 tened. The parietals are separated by the supraoccipital, but above 

 the supraoccipital there lie two sensory- canal scales of the transverse 

 commissural system which in old specimens (A and C) fuse with 

 the right and left parietals, and thus produce the efiect of a false 

 union of the two parietals over the supraoccipital (text-fig. 140 A, 

 p. 483). The posterior temporal fossa is large and completely roofed 

 in. Its inner wall is formed by the supra occij)ital and epiotic, its 

 floor and outei' wall by the postfrontal and squamosal, and its I'oof 

 by the frontal, parietal, squamosal, and epiotic. Its anterior end 

 is blind, and lies over the middle part of the postfrontal bone. 

 Hyrtl (I. c. p. 3) has pointed out that the great posterior temporal 



