466 



DR. AV. G. RIDEWOOD ON THE CRANIAL 



[Dec. 13, 



very shoi't and is united with the back of the supratempoi-al. 

 The supi-atemporal has the usual tiii-adiate aixangenient of the 

 sensory canal. 



The horizontal limb of the preopercular is a little more than 

 half as long as the upright limb, and makes with it an angle of 

 about 95 degrees. The interopercular is lai-ge, considerably larger 

 than the subopercular, and comes into direct contact with the 

 angular bone, without the intervention of the usual ligament. 



Gircuviorhital Series (text-fig. 1 27, p. 465). — There are nine bones 

 of this series. The nasal is roughly rectangular in shape, with a 

 narrow tube for the sensory canal passing lengthwise over its 

 surface. The form and relations of the other bones are readily 

 to be comprehended by a glance at text-fig. 127. 



Maxillary Series (text-fig. 127, p. 465). — The gape is very small 

 and bounded above by the premaxillse. The maxilla is only slightly 

 longer than the premaxilla. Fries (Scand. Fishes, ed. 2, ii. 1895, 

 p. 952) states that the premaxilla is longer than the maxilla in 

 the Chatoessinas, but such is not the case in the specimens now 

 under consideration. The front part of the maxilla is of con- 

 siderable vertical extent, and the posterior extremity is also 

 expanded. The premaxilla is flattened and scale-like, with a 

 sharp lower edge. Neither maxilla nor premaxilla bears teeth. 

 A single surmaxilla of small size is pi-esent on each side. 



Text-fig. 128 

 hnv 



CJiatoessus erehi, lij'opalatiiie arch, opercular bones, and mandible of left side, 

 mesial aspect. For explanation of lettering see p. 493. 



Mandihtdar Series (text-figs. 127 and 128). — The remarkable 

 shape of the mandible is doubtless due to the reduction of the 

 gape not being accompanied by an adequate forward displacement 

 of the quadrate-articular joint. The coronoid process thus comes 



