ABT. ly A MIOCENE PORPOISE FROM MARYIAND KELLOGG 35 



duTYi in its smaller size and also in the curvature of the anterior 

 and posterior margins, but otherwise the resemblance is rather 

 close. 



CERVICAL VERTEIBRAE 



No anl^losis between individual vertebrae (pi. 14) can be observed 

 in this cervical series, but the centra are crushed against one another. 

 They were not removed from the matrix for study, although direct 

 comparisons were made between them and those of Delphinodon 

 dividum, and all of their essential characteristics were determined in 

 this manner. Seven cervical vertebrae comprise this series. The 

 chief peculiarities observable in the cervical series toay be enumer- 

 ated as follows : Atlas of small size, its maximum length being about 

 one-half of its height, with low spine, strong inferior and vestigial 

 bladelike superior transverse processes, and well-developed hyapo- 

 physial process; axis with long thick spine, strong inferior transverse 

 processes and small odontoid ; neural spines of third to seventh 

 cervicals vestigial; inferior transverse processes of third to fifth 

 cervicals slender, directed obliquely backward, and those of the third 

 are more than twice as long as those of the fifth ; inferior transverse 

 processes of sixth cervical relatively large, directed nearly vertically 

 downward; inferior transverse processes of seventh cervical are 

 vestigial; axis and third to seventh cervicals, inclusive, exhibit a 

 longitudinal carina on inferior surface of centrum; foramen at base 

 of superior transverse process on sixth cervical much larger than on 

 any of the preceding; zygapophyses of third to sixth cervicals very 

 similar in size and shape, while those of seventh are much larger; as 

 regards height the centra of the third to seventh cervicals are all 

 about the same; epiphyses of all these vertebrae are very thin. 



Atlas. — The atlas differs from that of Delphinodon dividum not 

 only in its smaller size, but also in relative height. Another atlas 

 (pi. 12, figs. 3, 4) collected in zone 10 of the Calvert Cliffs has been 

 referred to this species. In general form, as viewed from in front, 

 these two atlases resemble the same vertebra in Sot alia. Both of 

 these fossil atlases are relatively long anteroposteriorly, their maxi- 

 mum lengths being about one-half of their height. The upper trans- 

 verse processes are merely blade-like crests arising along the pos- 

 terosuperior margin as in Delphinodon dividuTri, but the lower proc- 

 esses are relatively large. On the second atlas (pi. 12, fig. 3) the 

 facets for articulation with the occipital condyles are concave, broad- 

 er above than below, and are separated inferiorly by a rather wide 

 interval (11.2 mm.). The neural arch is very little elevated and 

 is narrow anteroposteriorly (11.9 mm.) near the spine. It is pierced 

 on each side by a vertebrarterial canal and bears a low blunt spine. 

 The lower transverse processes are short, thickened, and project 



