126 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 105 



being estimated as 70 mm. The right pedicle of the neural arch is 

 robust and the roof of the neural arch was apparently rather narrow 

 anteroposteriorly, inasmuch as the distance from the anterior margin 

 of the neural arch to the posterior margin of the postzygapophysial 

 facet is 24.5 mm. The prezygapophysial facets are distinctly impressed 

 on the dorsal surface of the diapophyses and slope from the outer to 

 the inner margin. The postzygapophysial facets are elongated (17.5 

 mm. in length) and slope obliquely downward and inward. The large 

 facet for the capitulum of the third rib is located obliquely on the 

 centrum at the upper posteroexternal angle. 



Other measurements, in millimeters, for the second dorsal are as 

 follows: Greatest anteroposterior diameter of centrum, 26.5; greatest 

 transverse diameter of posterior face of centrum, 46+ ; greatest vertical 

 diameter of anterior face of centrum, 31.5. 



Fourth dorsal: This vertebra (pi. 8, figs. 2, 6) differs from the 

 corresponding dorsal of Inia in having a more nearly circular instead 

 of subpyriform neural canal, a pronounced widening of the posterior 

 surface as contrasted with the anterior surface of the centrum, steeply 

 sloping prezygapophysial facets, the long axis of the facet for the 

 tuberculum on the diapophysis nearly vertical, and the large facet for 

 capitulum of fifth rib located obliquely on the centrum at the upper 

 posteroexternal angle. From the corresponding vertebra of Eurhino- 

 delphis this dorsal is distinguished by having shorter diapophyses, a 

 more nearly circular neural canal, and the posterior surface of the 

 centrum noticeably wider than the anterior face. Although the neural 

 spine is broken off at the base, the position and curvature of the 

 anterior edge suggest that it was rather broad anteroposteriorly. The 

 backwardly projecting dorsal portion of the neural arch is elongated 

 anteroposteriorly (36 mm. medially) and rather wide (42 mm.) . The 

 neural arch is robust, with a short diapophysis on each side which 

 bears a pyriform anticular facet for the tuberculum of the fourth rib. 

 The prezygapophysial facets are somewhat concave anteroposteriorly 

 and slope steeply from outer to inner margins. The postzygapophysial 

 facets are elongated and slope obliquely downward and inward. 



Sixth dorsal: Compared with the fourth dorsal, the backwardly 

 projecting dorsal portion of the neural arch is considerably nan'ower 

 and longer anteroposteriorly (40 mm.), the centrum is longer, and the 

 prezygapophyses are more elongated and narrower. The short dia- 

 pophyses (pi. 8, figs. 1,5) do not differ markedly either in position or in 

 size from those on the fourth dorsal, and the facets for the tubercula 

 of the sixth ribs are noticeably constricted ventrally. The concave 

 prezygapophysial facets are shorter and narrower dorso ventrally than 

 on the fourth dorsal, although the conformation and size of the 



