SKELETON OF EEGALECUS AE&ENTEUS. 29 



23. The mandible (figs. 6 and 14) is remarkably short and high (p. 15). 



24. The first and second branchial arches (fig. 17) are terminated dorsally Dy a 

 segment apparently not before described {pa.lr^, pa.by^), and which it is proposed to call 

 the parairancMal (p. 17). 



25. The copulse, or medio-ventral elements, of the branchial skeleton are eight in 

 number (fig. 17, cp. ^-cp. ^), of which the first (cj). ') is the entoglossal or basihyal ; of 

 the others, two (cp. ^ and cp. ^) join the ventral ends of the first and second arches 

 respectively, and are considered to be the only two true basibranchials ; the others are 

 intermediate, each between two arches, and it is therefore proposed to call them inter- 

 h'cinchials (p. 18). 



26. The vertebral column (fig. 5) consists of ninety-three vertebrae, with the neural 

 arches of which are connected two hundred and six interspinous bones, serving for the 

 attachment of two hundred and five (15 + 190) dermal fin-rays. 



27. There is a gradual increase in length of the vertebral bodies from before back- 

 wards, the first (fig. 20, c. 1) being ^o inch, the ninety-second (fig. 25, c. 92) 4 inches 

 in antero-posterior dimensions (p. 20). 



28. The atlas bears long transverse processes; the second vertebra is devoid of these, 

 which, however, reappear in the third (p. 20). 



29. Small slender ribs are borne by the eighth to the twenty-fifth vertebra inclusive 

 (p. 21). 



30. None of the haemal processes unite below, so that there are neither haemal arches 

 nor haemal spines in any part of the vertebral column (p. 22). 



31. The bone terminating the vertebral column posteriorly (PI. VI. fig. 25, c 93) is 

 considered to be a demivertehra, that is to represent the anterior half of a vertebra] 

 body ; it is in the same straight line with the rest of the vertebral column, so that the 

 tail is strictly diphycercal (pp. 22 and 23). 



32. In the anterior part of the body there is an average of two, in the posterior part, 

 of three interspinous bones to a vertebra (p. 23). 



33. The fin-rays are articulated to the interspinous bones not directly, but through 

 the intermediation of ovoid cartilaginous nodules (figs. 20 and 25, c.n), which alternate 

 with the interspinous bones and are considered to represent a second or distal set of 

 radials ox pterygiophores (p. 24). 



34. The anterior nine interspinous bones lie altogether in front of the atlas and 

 overhang the skull (&g. 2U) ; the first five of them are peculiarly modified and ankylosed 

 together to support the crest (p. 25). 



35. The posttemporal (PI. IV. figs. 6, 8, and 10, and PI. V. fig. 18, p.tm) is not forked, 

 and is closely applied to the dorsal surface of the skull, in a groove between the epiotic 

 and the pterotic (p. 26). 



36. There are three brachials (figs. 6 and 18, br. i~^) supporting the pectoral fin ; they 

 are irregular flat bones, having a vertical height equal to that of the scapula (p. 26). 



