324 Bulletin American Museum of Natural History. [Vol. XXIV, 



Although practically adult, it is slightly exceeded in size by all of the 

 others except one of the Iceland examples. 



Vertebral Column. The vertebral formula in this species seems subject 

 to slight variation, as is the rule with most animals, through variation in the 

 number of lumbars or caudals, which Mr. Andrews has found to vary in 

 two specimens taken at the same time and place on Long Island. The 

 total number seems to range from 55 to 57, with the average at 56, which 

 is the number in the Provincetown specimen, namely: C. 7, D. 14, L. 11, 

 Ca. 24 = 56. 



Cervical Vertebrae. The cervical vertebra (Plate XXII, Figs. D-H) differ 

 in several notable particulars from any of those thus far figured as belonging 

 to the genus Eubalcena, and are especially interesting as presenting a wonder- 

 ful degree of bilateral asymmetry. Viewed in profile the spinous processes 

 are united above from the 1st to the 5th inclusive, the 6th and 7th alone being 

 free, both as regards each other and those preceding them. Of the trans- 

 verse processes, those of the first cervical only are wholly free on both sides, 

 those of the others being united at their extremities into groups which may 

 be indicated as follows: left side, 1, 2, 3-4, 5-6-7; right side, 1, 2-3, 4-5-6-7. 

 In the first cervical the transverse processes have no inferior lamellae, but 

 they are developed from the 2d, 3d, and 4th on the left side, and from the 

 2d and 3d on the right. Those of the 2d and 3d on each side are united 

 basally; that of the 3d is much smaller and is free throughout its length. 



In viewing the cervical vertebrae from below, the 1st and 7th are seen to 

 be separated from the others by well-marked sutures, but there is no trace 

 of sutures, at least medially, between the other cervicals. 



The transverse processes of the atlas are rather short but very broad and 

 thick; that of the left side much heavier than that of the right, the whole 

 left half of the atlas being in fact very much more developed than the right, 

 as is distinctly seen in Plate XXII, Fig. E. The transverse processes of 

 the axis are rather longer than in the atlas, but many times more slender; 

 those of the succeeding vertebras decrease in length and size to the 6th ; the 

 7th is rather heavier than the 6th. 



A striking feature in the present example is the slight degree of ankylosis 

 between the atlas and the axis, which have actually coalesced at only three 

 points, namely : by a small portion of the centra at the base of the transverse 

 processes, and by the union of the neural spines. 



The cervical vertebrae of the type of B. cisarctica Cope are shown on 

 the same plate (Plate XXII, Figs. A-C) for comparison. They represent a 

 much younger and smaller specimen, with many differences in the details of 

 ankylosis. 



