268 



TELEOSTOMI 



The foramen magnum is bounded by paired exoccipitals at the 

 sides, and a median basioccipital below. In the Teleostei (Figs. 

 305, 381) a median snpraoccipital appears above (p. 326). The 

 exoccipitals, which are pierced by the glossopharyngeal, the vagus, 



Amia calva, L. (After Allis, slightly altered.) A, left-side view of the skull. B, left-side 

 view of the cranium, from which the dermal bones have been removed. Cartilage is dotted. 

 a. i:, auditory capsule ; mi, adnasal : ar, dermarticular ; as, alisphenoid ; 60, basioccipital ; bst, 

 branehiostegal ray; c, cartilaginous cranium; tl, dentary; ep, epiotic; cth, mesethmoid ; ex, 

 exoccipital ; /, frontal ; fa, foramen for facial nerve ; ff, foramen for vagus ; h, hyomandibular ; 

 iop, interopercular ; /, lachrymal; m.g, median gular; m.l, lateral line in mandible; mx, 

 maxilla; n, neural arch; na, nasal; n.sp, neural spine; 0, opisthotic ; ohs, orbitosphenoid ; 

 oc.11, foramen for spino-occipital nerve ; o.f, vacuity with optic foramen in front ; olf, olfactory 

 capsule; op, opercular; p, parietal; ji/, prefrontal; pmx, premaxilla ; po, prootic ; pob, post- 

 orbital; pop, preopercular ; pp, supratemporal ; pt, post - temporal ; ptf, postfrontal; q, 

 quadrate; -s pterotic ; s.a, supra-angular; svi, septomaxillary ; sop, subopercular ; spm, supra- 

 maxilla ; t.f, trigeminal foramen ; o.c, vertebral centrum. 



and the occipito - spinal nerves, replace cartilage of compound 

 segmental origin (p. 12). The basioccipital forms the floor of the 

 brain-cavity behind, develops round the anterior end of the noto- 

 chord, and corresponds to the vertebral centra situated farther back 



