14S ESCHRICHT AND REINHARDT 



transversely elongated aperture, one and a half inch wide and one inch high. A prominent 

 transverse ridge projects backwards into the cerebral cavity from the lower margin of this opening, 

 representing the pi-ocessus olwaris of anthropotoray ; below this is the concavity of the sella turcica. 

 The opening leads into a canal which runs directly forwards in the mass of cancellous bone formed 

 by the union of the frontal, ethmoid, and presphenoid, for a distance of eight and a half inches- 

 In the middle of its course it retains its original width, but is contracted in vertical diameter 

 to about half an inch, and has a longitudinal eminence in the median line of the floor. Between 

 five and six inches from the brain cavity it divides laterally to form the two somewhat dilated 

 chambers for the lodgment of the olfactory bulbs. Two inches behind the anterior wall of each 

 chamber a large oval canal (c), half an inch in its greatest diameter, passes off in an outAvard, 

 backward, or downward direction. This canal, probably for the transmission of a blood-vessel, 

 joins that which lodges the optic nerve at about ten inches from the cerebral cavity. The floor 

 of the front part of the rhinencephalic chamber slightly ascends, and with its small concave anterior 

 wall forms the cribriform plate of the ethmoid bone [b). This is little more than an inch in 

 extent in either direction, and the foramina in it are both smaller and less numerous than 

 in the corresponding part of the small fin-whale {Balænoptera rostrata), preserved in the 

 Hunterian collection. The foramina, pretty closely scattered over the anterior wall, extend 

 backwards along the floor of the cavity in three lines, one in the middle and one near each 

 side. 



In front of, or rather below, the cribriform plate is alarge chamber, of an irregularly triangular 

 shape. The base, or longest side of the triangle (fourteen inches), is nearly horizontal, and forms 

 the roof of the chamber. The floor, five inches long, and also closed, runs forwards and downwards, 

 and the anterior side forms an open, narrow slit, twelve inches in length, slightly curved, with the 

 concavity outwards, and opening into the roof of the great nasal passage, close to the side of the 

 vomer. This olfactory chamber is extremely narrow from side to side, though its breadth varies 

 in different parts, on account of the irregular disposition of its outer wall. In the middle part, 

 in front, where this is very prominent and convex, the space between the two sides of the cavity 

 is not more than a quarter of an inch. Posteriorly the outer wall is raised into several longitudi- 

 nally placed elevations of a very simple character, representing the ethmoid turbinal bones. Of 

 these the principal one is connected with the anterior or under surface of the cribriform plate. 

 The upper and lower recess formed by this are each subdivided by small ridges, resembling in 

 general disposition, but altogether smaller, and of more simple form, than those of Balænoptera 

 rostrata. 



The entire number of vertebrae is fifty-five, of which, adopting the division between the 

 lumbar and caudal regions used by Eschricht and Reinhardt, seven are cervical, twelve dorsal, 

 fourteen lumbar, and twenty -two caudal. The latter appear to be quite complete. 



The adjoining woodcut, showing a section through the middle line of the ankylosed mass of 

 the cervical vertebræ, well illustrates some points in the structure of these singularly modified 

 bones. The union of the seven bodies into one is very complete; even the layer of cartilage 

 between the sixth and seventh, described by the authors of the memoir, does not exist in this 

 specimen. Indeed, the separation of the last two bones is only slightly indicated near the lower 

 surface of the united bodies. The upper part of the arch will be seen to consist of three pieces, 

 the first composed only of the atlas, the second common to the axis and the four succeeding 

 vertebræ, the last formed of the seventh by itself. 



