OF BAL^NOPTERA MTJSCULUS. 



213 



would almost answer for this case were it not for the greater depression which the Boston 

 whale presents in the inferior surfece, and for a slight difference in the external border of 

 the lateral portions. The anterior surface has an articular portion of the usual shape cor- 

 responding to that on the posterior side of the atlas. The odontoid process (PI. vi, fig. 5 a), 

 is about 1-2 inch in height, and presents a depression in its summit like the crater of a vol- 

 cano. The posterior surface has a deep vertical depression in the middle, which is con- 

 tinued into a notch in the upper and lower sides. The two halves of the body share in the 

 inchnation of the transverse processes ; these are broad masses enclosing a large foramen 

 5 1-2 inches on the left side, 4 1-8 inches on the right, which shows of how little value 

 such features are for classification. The parapophysis, which forms the inferior boundary, is 

 broader and stouter than the diapophysis, which forms the upper. The transverse processes 

 are directed backward, as shown in fig. 7. Two tuberosities forward inclining, of which 

 the internal is the larger, separated by a slight groove, are seen on the superior edge of the 

 diapophysis over the foramen (PI. vi, fig. 5 6). The spinal canal has a breadth of 5 1-8 inches 

 to a height of 4 1-2. The arch presents a slight ridge in the median line, and a promi- 

 nence on either side projecting forward and upward ; that on the right is the larger. On 

 the anterior aspect of each of these prominences is a smooth plate (PI. vi, fig. 5 c), the real 

 zygapophysis ; the posterior ones (PL vi, fig. 6 a) are on the outer sides of the arch. 



The other cervical vertebrte show the usual amount of individual variation when com- 

 pared with descriptions and figures. The rings formed by the transverse processes are 

 complete in the 4th or 5th, and very nearly in the 3d. In the latter the interval is of only 

 about 1-4 inch on the right side ; on the left it cannot be accurately determined, as a small 

 piece has been broken off. In the 6th the inferior processes are very small, that of the 

 left side, however, being more than twice as large as its feUow. They exist in the 7th only 

 as shght ridges. After this description of the first two and slight sketch of the remaining 

 cervical vertebrae, it appears well to study in connection with the following table of meas- 

 urements the modifications which each element of a vertebra undergoes in the entu'e 

 column, and to compare them with those in other specimens. 



MEMOIRS BOST. SOO. NAT. HIST. VOL. II. 



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