12 



UNITED STATES NATIONAL MUSEUM BULLETIN 29 4 



lateral processes are broken off at the base. Pedicles of 

 ' the neural arch are ])reserved on the fourth, fifth, and 

 sixth cervicals, but all lateral processes except for basal 

 portions are missing on the centra. Both epiphyses are 

 firmly fused with the centra of all cervicals. Except for 

 I he fusion of the centra of the axis and the third c«rvical, 

 t he cervicals were free. The pedicles of the neural arch 

 of the third to sixth cervicals, inclusive, are low and 

 wider transversely than anteroi)ost€riorly. Shortening 

 of the pedicles, as indicated on the third cervical, and 

 flatteninp of tlie roof of the neural arch lias resulted in 

 an unusually low neural canal. On the third cervical the 

 upper transverse process is united distally with the ex- 

 tivmity of tlie lower process to enclose the large cervical 

 extension of the thoracic retia mirabilia, wliich also 

 passes through the foramen transversarium on the trans- 

 verse process of the axis. The atlas and axis are massive, 

 broad and thick, with a low neural spine which on the 

 atlas rises to a blunt apex. The atlas has a short rugose 

 hyapophysial process. Tlie odontoid process of the axis 

 is slender and abnormally elongated. The total lengtli of 

 the cervicals, including the cartilaginous intervertebral 

 disks, did not exceed 30.5 nun. (12 inches). See table 11 

 for measui-ements of the cervical vertebrae. 



Atlas. — This massive, broad and lliick atlas (USNM 

 23794) has a short, laterally compressed neural spine, a 

 liigli neural canal, and a nodular i-emnant of an upper 

 transverse process. The anterior facets (pi. 5, fig. 1) for 

 articulation with the occipital condyles of the skull ai-e 

 deeply concave, widest neai- the middle of their height 

 and separated ventrally by a shallow groove. The vas- 

 cular foramen which noi-mally pierces the neural arch 

 on each side is closed. The lower transverse process is 

 short, thick, and projects outward below the smaller, 

 nodular upper remnant. A short, broad, rugose hya- 

 pophysial process is present. An upward, forward slop- 

 ing concave surface (pi. 5, fig. 2) for reception of odon- 



toid process of the axis separates ventrally the reniform 

 articular surfaces for the axis. 



Additional measurements are as follows: greatest dis- 

 tance between outer margins of posterior articular 

 facets, 177 mm.; greatest vertical diameter of right pos- 

 terior articular facet, 83 mm. 



Axis.— On the right side of this axis (USNM 23794) 

 the transverse process is broken off at the base. The com- 

 plete left process (pi. 5, fig. 3) is elongated, bent 

 backward, and perforated by a large foramen trans- 

 versarium ; the lower bar of this process is very thick 

 (38 mm.) at the base and the upper is thin, anteropos- 

 teriorly compressed. The small neural canal is low, 

 wider (54 mm.) than high (37 mm.) . The neural spine is 

 reduced to a low thick anteroposterior ridge. The odon- 

 toid process is slender, unusually elongated and concave 

 dorsally at its distal end. The vertical diameter (right, 

 94 nun.) of the deeply concave anterior articular facets 

 exceeds the transverse diameter. The anterior median 

 angle of the neural arch is not extended forward, to 

 articulate with the neural arch of the atlas. The pos- 

 terior face of the centrum of the axis is fused with the 

 opposite surface of the third cervical as also the pedicles 

 of the neural arches of both cervicals. This fusion may 

 represent the initiation of the subsequent coalescence 

 of the cervical series of some mysticetes during later 

 geological time. 



Third cervical. — The broadly eliptical posterior face 

 of the third cervical (USNM 23794) is concave. The 

 pedicles of the neural arch are short, their minimum 

 wadth (39 mm.) greater than their ajiteropositerior di- 

 ameter (23 mm.). A marked increase in the transverse 

 diameter (67 mm.) of the neural canal (pi. 5, fig. 4) 

 characterizes this cervical. The slender upper trans- 

 verse process (diapophysis) on the left side projects 

 outward and downward from the pedicle of the neural 

 arch and is imited distally with the curved upward and 



Table 11. — Measurements {in mm.) of the cervical vertebrae, USNM 83794 



Greatest vertical diameter of vertebra, tip of neural spine to ventral face of cen- 

 trum 

 Greatest anteroposterior diameter of centrum 

 Greatest tranverso diameter of centrum anteriorly 

 Greatest vertical diameter of centrum anteriorly 

 Greatest vertical diameter of neural canal anteriorly 

 Greatest transverse diameter of neural canal anteriorly 

 Greatest distance between outer ends of diapophyses 

 Greatest distance between outer ends of parapophyses 

 Least anteroposterior diameter of right pedicle of neural arch 

 Greatest distance between outer margins of anterior articular facets 



Atlas 



Axis 



C.S 



C.4 



C.S 



• Dorsally ; >> Plus odontoid process ; ° Posteriorly. 



C.6 



