HIGH SCHOOL ZOOLOGY. 



21 



these kinds may be closely meorporatcd with those of the first 

 category. 



17. An inspection of the cranium from the upper surface 

 (Fig. 6) discloses in the middle line two slits (the anterior and 



pm 

 a 

 n 



Fig. C. — Cranium and Anterior Vertebrae of Catfish from above. 

 M. mesethmoid ; pm. premaxilla ; a. ajitorbital ; n. nasal; e. parethmoid ; _ fr. 

 frontal ; s. sphenotie ; p. pterotic ; ep. epiotic ; t. supraclavicle ; so. supraoccipital 

 spine ; 4. transverse process of fourth vertebra. 



posterior fontanelles) which separate the two frontal bones 

 except for a short intervening bridge, where these bones (which 

 form a consideraVjle part of the cranial roof) articulate by a 

 serrated suture. In front of the anterior fontanelle is the 

 mesethmoid bone* behind the posterior, the supra-occipital. 



