26 



Mystacoceti 



It will suffice to remark here that (i) the term Infra-class is substituted 

 for the word Section employed by Parker and Haswell, (ii) the two Orders of 

 marsupial animals are now accorded sub-ordinal rank only, and (iii) the Orders- 

 of Eutheria have been increased to fourteen in number. 



Without entering into a detailed description of the characters 

 of the several Orders, it will suffice to enumerate those of the 

 Sub-Classes and of the Sections. 



SUB-CLASS I. PROTOTHERIA. 



1. The vertebral centra lack epiphyses, or these are only 

 imperfectly developed. 



2. The bones of the skull coalesce early, by the obliteration of 

 the sutures (the skull thus resembling that of birds). 



3. A large coracoid, articulating with the sternum, is present. 



The pro-coracoid is distinct. Fig. 12. 



4. A T-shaped episternum is present. 



5. Two epi-pubic bones are present. 



6. A cloaca is present, into which the ureters and urinary 

 bladder open separately. 



7. The corpus callosum is not developed in the brain. 



8. The oviducts are distinct throughout. 



