SKELETON OF LEPIDOSTEUS. 449 



an upper and the superior face of a lower ossification in Meckel's 

 cartilage. . There are well-developed angular and " supra-angular " 

 bones, the latter curving in above the coronoid elevation. On 

 the inner side there is posterioi'ly a large laminar prsearticular, 

 which ossifies through the coronoid cartilage below the anterior 

 part of the supra-angular. In front of this a ridge of the dentary, 

 parallel to its margin, is covered by two elongate dentigerous 

 laminse, the shorter anterior one entering the symphysis, the 

 posterior ascending the coronoid elevation for a short distance 

 external to the prfearticular ; on one side a small bone is inter- 

 calated at the junction of these two bones, which may be termed 

 intra-dentaries. The preeai'ticular and intra-dentaries are often 

 termed collectively " splenials," but it is very improbable that any 

 of them is the homologue of the true splenial. 



The ptery go-quad rate is completely separated from the hyoid 

 arch, and supported by it only through the articulation of the 

 quadrate with the prjeoperculum. The ectopterj^goid is a very 

 long and stout bone ; anteriorly it articulates with the prse- 

 maxillary above the expanded head of the vomer ; the posterior 



Text-fiijuie 4. 



Lepidosfezis platystoniits. Orbitosplienoid (os.), alisphenoid {as.), and pro-otic 

 {pro.) bones ; pas. paraspbeuoid. Lateral view. 



seven segments of the maxillary are firmly united to its outer 

 face, which ,has a groove for their attachment ; the long laminar 

 palatine is attached to its lower surface. The entopterygoid is 

 small, the metapterygoid bears a process for articulation with 

 the parasphenoid and pro-otic, and the quadrate has an anterior 

 condyle for articulation with the lower jaw and a posterior one 

 for articulation with the anterior end of the pr£eopex'culum. " 



The large interoperculum is rigidly attached to the hyo- 

 mandibular, symplectic, and praaoperculum ; the last-named is 

 reduced to a small bone that lies above the anterior part of the 

 interoperculum and ends in a concave facet for articulation with 

 the quadrate. Collinge and Allis transpose the names of the 

 preeoperculum and interoperculum, on the ground that the latter 

 is attached to the hyomandibular and transmits a branch of the 

 sensory canal system. It may be pointed out that the inter- 

 operculum is quiLe normal in its relation to the suboperculum 

 behind and the lower jaw in front, and that where it is in 



