176 ON THE MORniOLOGICAL CONSTITUTION OF 



must be the zygopophyses of the succeeding cranial segment. 

 These occipital and temporal jugular articular processes, like 

 the corresponding processes in the column below, present 

 distinct cartilaginous articular facets, and are contiguous to 

 the "foramina lacera posteriora" or "intervertebral fora- 

 mina," formed by the conjunction of the temporal and 

 occipital jugular fossre, and which transmit, as in the spine, 

 vessels and nerves. But the petrous portion of the human 

 temporal bone has, in addition, a pair of distinct pro-zygo- 

 pophyses. They are situated on the anterior margins of the 

 petrous portions, where these margins form the angles with 

 the squamous portions, in which are situated the openings of 

 the Eustachian tubes. The articular surfaces of these pro- 

 cesses are perpendicularly striated, and are applied against 

 corresponding surfaces of the so-called styloid processes of 

 the sphenoid at the posterior angles of its great wings. These 

 " styloid processes " are therefore the zygopophyses of the 

 post-sphenoidal sclerotome. The pro-zygopophyses of the 

 post- sphenoidal and the zygopophyses of the pre-sphenoidal 

 may be observed at the fore part of the pterygo-palatine groove 

 in the fcetal bone, but are more remarkably developed in the 

 young ruminant ; in which also may be observed the zygo- 

 pophyseal connection of the pre-sphenoidal with the ethmoidal 

 neurapophyses. 



AVe have, therefore, in these zygopophyseal connections 

 distinct evidence of five cranial segments — an ethmoidal, pre- 

 sphenoidal, post-sphenoidal, temporal, and occipital — in addi- 

 tion to the vomerine and rhinal. 



For the further development of this subject, the cranium 

 of a cyprinoid fish should next be selected. If the lateral 

 wall of the cranium be examined, either from the external or 

 mesial aspect, five serially-arranged neurapophyseal plates 

 will be recognised, connected to one another by four distinct 

 zygopophyseal articulations. These plates are, from before 



