from the Coal Measures of Nova Scotia, 2 LI 



do not taper off and ramify, as in the bones of fishes, nor anastomose 

 with the corresponding tubes from the neighboring cells, although in 

 one of the longitudinal sections there are a few indications of such 

 a connection. Some of the other sections examined show a larger 

 number of canaliculi ; but generally there are only a few 

 of these tubes attached to each lacuna, and in some cases they 

 appear to be entirely wanting. As the canaliculi vary 

 much in number in different saurians, and also with the age of 

 the animal, their paucity in this case is not remarkable. It is 

 possible, however, that the method employed in preparing the 

 sections was not well adapted to rendering these minute tubes 

 visible. In a part of the transverse section a structure is 

 seen, which is quite different from the surrounding osseous 

 substance. This may be due to the presence of a small 

 cavity in the bone before the introduction of the mineral 

 matter, or to an imperfect ossification at that point : more prob- 

 ably the latter, as these vertebrae, like those of the PlesiosauruSy 

 show in their interior structure a degree of ossification somewhat 

 inferior to that at the articular terminal surfaces. 



It will readily be seen from the previous description, that a very 

 close resemblance exists between these vertebrae and those of the 

 Ichthyosaurus. This is especially noticeable in their flattened and 

 sub-hexagonal form, in their deep and regular terminal concavities^ 

 and in the separate state of the neural arch. The differences 

 which exist, however, although of much less importance, must not 

 be disregarded. The most marked of these have already been 

 alluded to; and may be seen in the absence from the sides of the 

 centrum of costal articular surfaces, in the deeper concavities at 

 the vertebral extremities, and in the form and dimensions of the 

 superior arch. The first of these differences would alone be 

 deemed sufficient, by the highest authority, to establish a distinction 

 between these remains and the vertebra3 of the Ichthyosaurus; 

 for in that genus, according to the statement of Prof. Owen, which 

 is peculiarly applicable to the present case, — " The lower tubercle 

 for the attachment of the rib never wholly quits the centrum : 

 any detached vertebral centrum therefore that might be dis- 

 covered, which had no lateral tubercle or articular surface for a 

 rib, might be safely pronounced, whatever the form of its anterior 

 and posterior articular surfaces, not to have belonged to a true 

 Ichthyosaurus, provided it was not compressed laterally, as in the 

 small terminal ribless caudal vertebrie which supported the caudal 



