D. Prepare the skeleton of the skate, 

 1. The skull, note — 



(a) The four labial cartilages on each side, the first supporting the lateral flap 

 of the fronto-nasal process, the second on the outer margin of the naso- 

 buccal groove, the third forming the internal, and the fourth the external 

 margia of the nasal aperture. 

 (6) The flat floor of the skull. 



(c) The roof, with the anterior and posterior fontanelles. 



(d) The foramen magnum. 



(e) The two rounded occipital condyles. 



(/) The indentation for the odontoid process of the vertebral plate. 



(g) The anterior projecting rostrum. 



(h) The pair of rostral cartilages at the sides of the rostrum. 



(i) The nasal capsules. 



(j) The auditory capsules. 



(k) The following apertures on one side — 



(1) In the region of the eye a large aperture for the optic nerve. 



(2) Some minute apertures over the optic foramen for the passage of 4th 



nerve. 



(3) Behind the optic foramen a small aperture for 3rd nerve. 



(4) Anterior to the auditory capsule the aperture for 7th nerve. 



(5) Above and anterior to (4) the aperture of 5th nerve. 



(6) In the lower posterior part of the auditory capsule, the aperture for 



10th nerve. 



(7) External to (6) the aperture of 9th nerve. 



(8) Two apertures in the nasal capsule for the passage of the orbito-nasal 



and the palato-nasal divisions of 5th nerve. 



(9) On the surface of the posterior part of skuU the apertures of the 



aqueducti vestibuli. 

 Make a sketch of the skuU from above, from below, and from the side. 



