4L PROCEEDINGS OF THE NATIONAL MUSEUM vol.69 



LUMBAR VEUTEBKAE 



All of the lumbar vertebrae are incomplete and none retains the 

 transverse process on the right side. Of the anterior lumbars there 

 are three that are more or less complete and two others are repre- 

 sented by the left transverse process ; these five lumbar vertebrae rep- 

 resent a consecutive series. All of the intervening lumbars between 

 these and the two that constitute the end of the series are lost. The 

 neural spine and right transverse process are not preserved on the 

 last lumbar and with the exception of the left transverse process all 

 of the second from the last is missing. When complete the lutabar 

 series probably consisted of nine or ten vertebrae. The centra are 

 all longer than broad and progressively increase in length from the 

 anterior one backward. Judging from the centra of the two anterior 

 lumbars and the last lumbar, all of them have a more or less distinct 

 median inferior carina. The transverse processes are as long as 

 the neural spines, very thin, and taper to the distal end which is 

 expanded anteroposteriorly. The transverse processes of the an- 

 terior lumbars are inclined forward and those of the posterior ones 

 backward. The neural arches and the neural spines are preserved on 

 the three anterior lumbars. The neural spines are nearly vertical, 

 relatively broad anteroposteriorly, with their expanded extremities 

 rather squarely truncated. The neural arches of the anterior lum- 

 bars are vertical, but those of the posterior lumbars are inclined 

 forward. The minimum anteroposterior diameter of the neural arch 

 is slightly less than one-half the length of the centrum, but each 

 neurapophysis is slightly wider at the base. The neural spine is 

 broader anteroposteriorly than the neural arch. The thin lamina- 

 like metapophyses are directed obliquely upward and forward ; their 

 superior margins are convex and their inferior margins are angu- 

 late. There are no distinct anterior and posterior zygapophyses. 

 The epiphyses of the posterior lumbar are very slightly if at all 

 thicker than either of those on the anterior lumbar. 



The lumbars of this fossil porpoise, as compared with those of 

 Delphinodon dividum, have more elongated centra, broader neural 

 spines, larger metapophyses, and the transverse processes have ex- 

 panded extremities in contrast to the slender type of the latter. 



First Imnhar. — The distal extremity of the neural spine and the 

 major portion of the right transverse process are missing (pi. 9, 

 fig. 4), but only the tip of the right metapophysis is damaged. The 

 centrum is slender, constricted mesially, and exhibits a faint median 

 inferior carina. Both epiphj^ses are attached to the centrum. The 

 left transverse process is slender, slightly expanded at the extremity, 

 but with the anteroexternal angle obliquely truncated and rounded 

 off. The superior margin of the large metapophysis turns sharply at 



