ART. 14. MARYLAND FOSSIL POEPOISE KELLOGG. 27 



The stylohyals (pi. 9, figs. 2-3) are decidedly more like those of 

 Inia than those of Platanista. Each is an irregular elongate bone, 

 slightly curved upward and suddenly curving forward at the distal 

 end. The anterior edge for its greater part is rounded and the 

 posterior margin compressed so that a cross section of the stylohyal 

 would be somewhat ovoidal. These bones are ^arly a third again 

 as long and twice wider than are the flattened stylohyals of Inia 

 geojfrensis. 



Measurements of the hyoid hones. 



mm. 



Greatest length of central portion (basihyal) 36.0 



Antero-posterior width across ceratohyals (outside measurement) 36.5 



Greatest thickness of thyrohyal at distal end 9.0 



Greatest breadth of thyrohyal 49.0 



Greatest length of thyrohyal (postero-internal margin to tip) 107.5 



Greatest length of left stylohyal 153. 5 



Greatest breadth of left stylohyal 21. 5 



CERVICAL VERTEBRA. 



All of the cervical vertebrae except the atlas are missing. The 

 atlas is complete and agrees in some respects with the cervical de- 

 scribed by Cope and by Case ® as Priscodelphinus grandaevus^ but is 

 much larger. While agreeing with the atlas of Inia geojfrensis in 

 the presence of both upper and lower transverse processes, it differs 

 in many details of form, some of which may be attributed possibly 

 to individual variation. The atlases of Liyotes and Platanista have 

 lost the upper transverse process (diapophysis) and the lower one 

 (parapophysis) is considerably shorter. In the living river dolphins 

 a free atlas is accompanied by separated cervicals. 



This fossil atlas is relatively deep antero-posteriorty, the length 

 (66 mm.) being about one-half of the greatest breadth (113.5 mm.) 

 across the anterior articular facets. The facets for the occipital 

 condyles (pi. 12, fig. 4) are concave, broader above than below, and 

 inclined obliquely outward. They are separated inferiorly by a 

 rather wide interval (18 mm.). The neural arch is not strongly 

 elevated and is broad antero-posteriorly. On either side the neura- 

 pophysis (pi. 8, fig. 5) is pierced by a large elliptical vertebra- 

 arterial canal. The neural arch may have borne a low, blunt spine 

 for a longitudinal rugose area which appears to represent its base 

 is present. 



The upper and lower transverse processes project backward. The 

 upper transverse process is broad and flattened dorso-ventrally ; the 

 posterior margin is rounded while the anterior is thin and blade-like. 



3 Case, E. C, Miocene Text, Maryland Geol. Suiv., Baltimore, p. 15, pi. 12, figs, la, 

 lb, Ic, 1904. 



