AFFINITIES. HABITS. 561 



There is a pair of bones representing the pelvis and connected 

 \vith the transverse processes of the last precaudal vertebra, but 

 in no hving species is there a trace of a femur. The lips are 

 tumid and provided with stiff bristles. Salivary glands are 

 well developed. The stomach is divided into two portions, of 

 which the cardiac is provided with a gland and the pyloric 

 usually with two caeca. The large intestine has a caecum. 

 The apex of the ventricle is cleft, and there are two superior 

 venae cavae. Extensive retia mirabilia are formed. The 

 diapliragm is extended very obliquely far back into the ab- 

 domen, so that the pleural cavities are prolonged dorsally 

 to the viscera, but the heart lies in the sternal region. The 

 brain is small and but little convoluted. The testes are 

 abdominal ; the uterus bicornuate and the placenta zonary (in 

 HaUcore). 



As will be gathered from this account, the Siren ia present no 

 important resemblance to whales. They differ in almost all 

 the cranial features and in the dentition ; in the structure of 

 the well-jointed anterior limb ; in the absence of a prolongation 

 of the epiglottis and arytenoid cartilages into the nasal pas- 

 sage ; in the small size and slight convolution of the brain. 

 The whale-like features are the reduction of the nasal bones, 

 the short neck, the form of the tail, and the absence of posterior 

 limbs. By some they have been supposed to be allied to the 

 Ungulata, but save in the form of the molar teeth in Manatus, 

 it is difficult to point to any resemblance. The affinities to 

 the Proboscidea are explained on p. 571. 



There are two living genera, but a third genus Rhytina only 

 became extinct in the eighteenth century, and we have des- 

 criptions of its appearance and soft part. They are purely 

 aquatic and never come on to the land. They inliabit shallow 

 seas near the coast, estuaries, and rivers which they ascend 

 sometimes almost to their source. They feed on sea- weeds 

 and aquatic plants. They are gregarious, slow, inoffensive, 

 gentle creatures, quahties which render them an easy prey to 

 the hunter, and which brought about the entire destruction of 

 the Rhytina. They are sought after for their flesh as food, 

 for the oil derived from the fat beneath their skins and for 

 their hides. They use their limbs as hands for conveying food 

 to the mouth, and they are said to carry their young pressed 



