16 



UNITED STATES NATIONAL MUSEUM BULLETIN 294 



level of the anterior end of the centrum ; distinct prezy- 

 urupopliysial facets are not developed. 



Elkvkntii doksal. — Wide, dorsoventrally compressed 

 l)arapophyses, which project outward from near the 

 middle of the external surface of the centrum, a broad 

 distully truncated backwardly slanting neural spine, 

 (pi. 8, fig. 10) which rises 137 mm. above the roof of 

 the neural canal, and long (right, minimum length, 

 68 mm.) thin pedicles of the neural arch characterize 

 this vertebra (USNM 23794). Each parapophysis has 

 a thick concavely curved posterior edge, a thin rounded 

 anterior edge on distal half of its lengfth, and an ovoidal 

 (right, length 50 mm.) facet for head of eleventh rib 

 located posteriorly on extremity. The large metapoph- 

 yscs (pi. 7, fig. 10), separated anteriorly by an interval 

 of 38 mm., project forward l)eyond the level of the an- 

 terior face of the centrum. The elliptical profiles of the 

 anterior (pi. 6, fig. 10) and posterior ends of the centrum 

 are quite similar as are also their vertical and trans- 

 verse diameters. No protruding bony excrescences at- 

 tributable to osteophj^tosis are present on this vertebra. 



Twelfth dorsal. — Rather wide (minimum diameter, 

 65 mm.) and dorsovent rally compressed parapophyses 

 project outward from near the middle of the external 

 surface of the centrum (USNM 23794) ; the anterior 

 and posterior edges of this process are thin and the 

 extremity is obliquely truncated from the anterior edge 

 to the posterodistal angle, which is thickened but not 

 otherwi.se modified for attachment of the head of the 

 twelfth rib. The large laterally compressed metapoph- 

 yses (pi. 10, fig. 1) rise 60 mm. above the floor of the 

 neural canal and are separated anteriorly by an interval 

 of 40 mm. ; they project forward noticeably beyond the 

 level of the anterior face of the centrum. The distally 

 truncated neural spine (pi. 8, fig. 11) is inclined more 

 strongly backward and rises 125 mm. above the roof 

 of the neural canal. This vertebra (pi. 6, fig. 11) has the 

 narrowest (width, 38 mm.) and the highest (39 mm.) 

 neural canal of all the dorsal vertebrae. No protruding 

 bony excrescences are present on this vertebra. A prom- 

 inent longitudinal median ridge extends the length of 

 the floor of the 7ieural canal. 



LUMBAR VERTEBRAE 



The cervicals, the dorsals, and the nine anterior lumbars 

 comprising the anterior portion of the vertebral column 

 (USNM 23794), were found to lie in normal sequential 

 contact with one another. Behind the ninth lumbar the 

 tail portion of the skeleton, and at least two or possibly 

 three of the lumbars, was broken off and presumably 

 washed forward alongside the dorsal vertebrae, but re- 



versed so that the terminal caudal was almost on a line 

 with the cervicals. Two of the posterior lumbars were 

 displaced ; one lay between the rows of dorsal and caudal 

 vertebrae and the other was almost in contact with the 

 first of the twelve consecutive caudal vertebrae. Since 

 twelve lumbar vertebrae nonnally comprise the lumbar 

 series of the Calvert cetotheres, the disassociated verte- 

 brae was either the tenth or the eleventh. On the basis 

 of measurements, the displaced vertebra is regarded as 

 the tenth, the lumbar almost in contact with the first 

 caudal as the twelfth, and the eleventh as missing. 



The epiphyses are firmly ankylosed to the centrum of 

 all these lumbar vertebrae. Except on the posteriormost 

 lumbar no protuberant bony excrescences are present. 

 Arranged in serial sequence the centra of these lum- 

 bars increase in length, width and height from the an- 

 terior to the posterior end of the series. No median 

 longitudinal ridge or keel is developed on the first lum- 

 bar ; this ridge is rather faint on the second lumbar, but 

 increases in prominence toward the posteriormost lum- 

 bar. The parapophyses decrease in length from the first 

 to the twelfth lumbar. The thin pedicles of the neural 

 arch attain their greatest anteroposterior diameter 

 (minimum, 73 mm.) on the sixth lumbar. The transverse 

 diameter of the neural canal and the length of the meta- 

 pophyses diminishes from the anterior toward the pos- 

 terior end of the series. Neither pre nor postzygapophys- 

 ial facets are developed on these lumbars. Backward 

 slanting neural spines increase in height from the first 

 to the sixth lumbar and then become progressively 

 shorter before a more abrupt decrease reduces their 

 height to that of the first caudal. 



Circumstances of preservation including localized 

 pressure from weight of overlying strata on sediments 

 of unequal consistency in which the vertebral column 

 was embedded resulted in the tilting of the neural spine 

 leftward and the partial collapse of the left pedicles of 

 the neural arch and the sequential deformation of the 

 neural canal from the third, fourth, fifth, and to a lesser 

 extent the sixth lumbar. 



The total length of the consecutive series of twelve 

 lumbar vertebrae, including the cartilaginous interverte- 

 bral disks, did not exceed 1375 mm. (54% inches). See 

 table 13 for measurements of the lumbar vertebrae. 



First lumbar. — This vertebra (USNM 23794) was 

 excavated in normal sequential contact with the twelfth 

 of the consecutive dorsal vertebrae and hence is un- 

 questionably the first lumbar. No ventral longitudinal 

 ridge or keel is developed on the centrum and the out- 

 line of the anterior end (pi. 9, fig. 1) is more ovate than 

 elliptical. An increase in the length of the parapophyses 

 and in the height of the backward slanting neural spine 



