122 GILL, SYNOPSIS OP THE 



1. SYNOPSIS. 

 SUBORDERS. 



I. Intermaxillaries expanded forwards, normally inter- 

 posed between the maxillaries, and forming the ter- 

 minal as well as anterior portion of the lateral mar- 

 gin of the upper jaw. Nasal apertures produced 

 more or less forwards. Teeth of the intermaxilla- 

 ries apparently in normal number (3+3), conic; of 

 the maxillaries, 2- or 3-rooted. ZEUGLODONTIA. 



II. Intermaxillaries narrowed forwards, forming only 

 the point of the lower jaw, and underlaid by the 

 maxillaries, which form the entire lateral alveolar 

 margins of the jaw. Nasal apertures far back, near 

 the vertex. Teeth (when present) all single rooted. 



1. Teeth persistent after birth. Upper jaw without 



baleen. Kami of lower jaw united by a symphi- 

 seal suture. Olfactory organ rudimentary or ab- 

 sent ; the nasal bones being appressed on the fron- 

 tals and overlapped distally. DENTICETE. 



2. Teeth absorbed and disappearing before birth. Up- 



per jaw provided with plates of baleen. Kami of 

 lower jaw not united by suture. Olfactory organ 

 distinctly developed ; the nasal bones projecting 

 forwards, and free at their distal ends. MYSTICETE. 



ZEUGLODONTIA. 



FAMILIES. 



I. Anterior nares open forwards ; nasal bones elongated. 



BASILOSAURIIXE. (I.) 

 II. Anterior nares open far behind ; nasal bones short. 



CYNOHCIIXSS. (H.) 

 I. BASILOSAUEIDJE Cope. 



II. CYNORCro^E Cope. 



DENTICETE. 



FAMILIES. 



A. Rostrum of skull with a rounded apex. 

 I. Upper jaw rostrated and attenuated, or ledge-like 

 around the margin. Skull with the vertex pro- 

 duced forwards. Supraoccipital not projecting 



