No. 472] ANATOMY OF CRYPTOBRANCHUS 



293 



The distal end of the squamosal is firmly united with the enlarged 

 end of the quadrate, and partially overlies that bone. Ventrally 

 the squamous articulates with the posterior border of the ptery- 

 goid as has been described. 



The quadrate hones (Q.) are two small bones that form almost 

 the entire articular surfaces for the lower jaw. A small portion 

 of these surfaces, however, is formed by the pterygoids. Each 

 quadrate is a small, triangular bone lying at the distal end of the 

 squamous above described, and largely covered by it. The heavy, 

 basal portion of the bone projects beyond the end of the squamous 

 and, together with the tip of the pterygoid, is covered with a thick 

 pad of cartilage for articulation with the lower jaw. The slender, 

 medially projecting portion of the bone lies anterior and ventral 

 to the squamous, and dorsal to the pterygoid. It is more closely 

 attached to the former than to the latter bone. Osawa figures the 

 quadrate in the adult skull as entirely of cartilage, and describes 

 it with the cartilaginous cranium, but in the present form it is quite 

 fully ossified. 



The tympanic bones, described by Osawa in the Japanese spe- 

 cies, could not be determined. 



The exoccipiials (O.) form the greater part of the border of the 

 occipital foramen. Each bone presents a postero-laterally pro- 

 jecting condyle, for articulation with the first vertebra. Through 

 the base of this condyle passes a horizontal canal of considerable 

 size into the posterior part of the cranial cavity. This canal is 

 probably for the exit of the vagus nerve. The anterior part of the 

 exoccipital is much enlarged and is hollowed out to form the pos- 

 terior half of the auditory capsule. The dorso-anterior borders 



while the ventral border articulates with tht> postcM-ior cud of the 

 parasphenoid. 



angular in outline, esptu ially when seen from the dorsal aspect. 

 The ai>e\ of the irianiile, which lies at the posterior end of the 

 sao-itt:il ^,if,,,-.> i< ,li...,,u... i„ front of the base, so that the 



