144 SPECIMENS OF SIRENIA. 



intestine ; two csecal appendages open into the commencement of the 

 colon in Manatus, but in Halicore the csecum is simple. The 

 kidneys are simple and not raultilobate as in the Cetacea. The 

 placenta in the Dugong is arranged as a zone, and the villi are not 

 diffused over the surface of the chorion as in the Cetacea. In the 

 shape and arrangement of the teeth and in their order of succession 

 the Sirenia contrast strongly with the Cetacea. The incisor and 

 molar teeth are separated from each other by a wide interval. The 

 bones are dense and heavy ; the anterior nares are large and set 

 back. The vertebrae are not fused together to form a sacrum ; in 

 their ossification they do not form plate-like epiphyses. Chevron 

 bones are developed in the anterior caudal region. In Manatus there 

 are only six cervical vertebrae. As in the Cetacea, the clavicles are 

 not developed. The carpus is short, but has some breadth. 



Three families are recognised in the order Sirenia : Halicoridee, 

 Manatidae, Rhytinidae. The Museum contains twenty-two specimens. 



