SKELETON. 



497 



jecting from each side. Articulated to the distal ends of 

 the transverse processes are the downward curving ribs, and 

 also more delicate intermuscular bones which curve upwards. 

 In the caudal vertebrae, the centra (c.) bear not only 

 superior neural processes (n.a.), but also inferior haemal 

 processes (h.a.\ 



At the end of the vertebral column lies a fan-shaped 

 hypural bone which helps to support the tail. The fin rays 

 are jointed flexible rods, which in the dorsal and anal fins are 

 attached to the ends of interspinous bones alternating with 

 the neural and haemal spines, and 

 attached to them by fibrous tissue. 

 The Skull includes the following 

 bones, which may be grouped in 

 the following regions (the mem- 

 brane bones in italics) : 



(a) Around the foramen magnum ; 

 basi-occipital, two ex-occipitals, and 

 a supra- occipital. 



(b) Along the roof; .r^ra-occipital, 

 parietals, frontals, mesethmoid, 

 nasals. Beneath the parietals lie 

 the alisphenoids. 



(c) Along the floor ; basi-occipital, 

 parasphenoid, vomers. 



(d) Around the ear on each side ; 

 sphenotic, pterotic, and epiotic 

 above, prootic and opisthotic 

 (beneath). 



(e) In front of and around the orbit ; 

 Parethmoid, lachrymal, orbitals. 



The first or mandibular arch is believed by many to form 

 Meckel's cartilage beneath, and the palato-pterygo-quadrate 

 cartilage above. Meckel's cartilage becomes the foundation 

 of the lower jaw, and bears a large tooth-bearing membrane 

 bone the dentary, a small corner bone the angular, while 

 the articular element is a cartilage bone. Of the bones 

 associated with the upper part, the palatine lies in front, the 

 quadrate articulates with the lower jaw ; while between 

 palatine and quadrate lie the pterygoid, the mesopterygoid, 

 and the metapterygoid. 



The second or hyoid arch is believed by many to form 

 the hyomandibular and the symplectic above, and various 



32 



FIG. 1 66. Caudal verte- 

 bra of haddock. 

 n.a., Neural arch ; c., centrum ; 

 h. a., haemal arch. 



