CETOTHERES FROM THE MIOCEISTE CHOPTANK FORMATION 



27 



caudals, each series being arranged when found in close 

 natural contact with the preceding and succeeding 

 vertebrae. The lumbar series comprised at least 12 lum- 

 bars of which the first and the two at the hinder end 

 were excavated in their natural sequence with the ad- 

 jacent part of the vertebral column. 



The total length of this skeleton, including the skull 

 (estimated length, 1525 mm.; 60 inches), from extrem- 

 ity of the rostrum to and including the terminal caudal 

 did not exceed 19 or 20 feet. 



CEKVICAL VEETEBRAE 



All cervical vertebrae are free and the epiphyses are 

 firmly ankylosed to their centra. Atlas not unusually 

 thickened with short neural spine; short, blunt trans- 

 verse processes; and almost vestigial hyapophysial proc- 

 ess. Axis has a short threesided neural spine; odontoid 

 process is short, acutely pointed; the broad transverse 

 processes are elongated, attenuated distally, turned 

 downward and bent backward; and the foramen trans- 

 versarium is reduced to a small opening. Upper and 

 lower transverse processes of third cervical elongated 

 and united externally to enclose a large cervical exten- 

 sion of the thoracic retia mirabilia; anterior face of 

 centrum is broadly elliptical, bluntly rounded laterally; 

 and neural spine short. Extremities of upper and lower 

 transverse processes of fourth cervical are not united 

 distally to completely enclose tlie foramen transversa- 

 rium ; laeural spine short, compressed from side to side, 

 and triangular in outline. Extremities of upper and 

 lower transverse processes of fifth cervical are separated 

 by a rather wide gap ; neural spine short, similar in con- 

 figuration to tliat of fourth cervical. Contour of anterior 

 face of centrum of sixth cervical nearly subcordate; up- 

 per slender transverse process is curved downward and 



backward to its attenuated extremity; no vestige per- 

 sists of lower transverse process; neural spine is higher, 

 attenuated distally. The diapophysis of the .seventh cer- 

 vical terminates distally in an elongated facet for artic- 

 ulation with the head of the anterior limb of the as- 

 sumed bifurcated first rib; no vestige of the lower 

 transverse process persists. 



The lower transverse processes (parapophyses) are 

 not developed on either side of the sixth and seventh 

 cervical vertebrae. The presence of an articular facet 

 at the extremity of each upper transverse process (di- 

 apophysis) of the seventh cervical vertebra points ei- 

 ther to the persistence of a separate cervical rib, or to 

 a cervical rib ankylosed to the first rib, the head of the 

 latter articulating with the diapophysis of the first dor- 

 sal vertebra. 



When the first rib is subdivided at its vertebral end 

 by a deep cleft into two distinct heads, the anterior limb 

 of this double-headed rib articulated with the end of the 

 upper transverse process (diapophysis) of the seventh 

 cervical vertebra and the posterior limb articulated only 

 with the diapophysis of the first dorsal vertebra. The 

 presence of a bifid first rib seems to be normal in occur- 

 rence in the Recent Balaen-optera boj'ealis. This forked 

 or bifurcated condition of the vertebral end of the first 

 rib has been reported also for other Recent Mysticeti. 

 The cervical rib may enther persist free or be ankj'- 

 losed with the first rib, and in the latter condition the 

 vertebral end of the first rib is bifurcated bj^ a cleft of 

 varying depth. Turner (1871), however, concluded that 

 the presence of a double-headed first rib has not neces- 

 sarily any specific importance. 



The total length of the seven cervical vertebrae com- 

 prising the neck, including cartilaginous intervertebral 

 disks, is 365 mm. (I41/2 inches). See table 19 for meas- 

 urements of the cervical vertebrae. 



Table 19. — Measurements {in mm.) of the cervical vertebrae, USNM S3636 



Anteroposterior diameter of the centrum 

 Transverse diameter of centrum anteriorly 

 Vertical diameter of centrum, anteriorly 

 Tip of neural spine to ventral face 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 transverse diameter of centrum, posteriorly 

 Greatest vertical diameter of centrum, posteriorly 



Atlas 



73 

 196. 5 



135 



71 



45 

 196.5 



60 



Axis 

 70o<i 



166 

 42 

 56 



235 

 34 



107 

 73 



C.3 



C.4 



C.5 



C.6 



C.7 



"^ Including odontoid process. 



