94 



above only as elongated hook-shaped borders produced backwards 

 around the maxillaries. (Delphinoidea.) 



1. Lachrymal bones coalesced with the jugals. 



a. Costal cartilages not ossified. The tubercular and capitular 

 articulations of the ribs blending together posteriorly. (Flower.) 



al. Maxillary bones with crests null or little developed. Teeth in 

 great part witli a complete cingulum, or a distinct tubercle at the 

 base of the crown. Eye moderate. External respiratory aperture 

 transversely crescentiform. 



INIIDAE. (LXVI.) 



a2. Maxillary bones with large bony incurved crests. Teeth with- 

 out cingulum or tubercle. Eye rudimentary. External respira- 

 tory aperture longitudinal. 



PLATANISTIDAE. (LXVII.) 



b. Costal cartilages firmly ossified. Posterior ribs losing their capitu- 

 lar articulation, and only uniting with the transverse processes of 

 the vertebrae by the tubercle. (Flower.) 



DELPHINIDAE. (LXVIII.) 



2. Lachrymal bones distinct from the jugals. 



a. Costal cartilages not ossified. The hinder ribs losing their tuber- 

 cular, and retaining their capitular articulation with the vertebrae. 

 (Flower.) 



ZIPHIIDAE. (LXIX.) 



B. Head not rostrated or marginated ; snout high towards the front 

 and projecting beyond the mouth. Skull raised behind and retrorsely 

 convex. Supraoccipital projecting forwards laterally to or beyond the 

 vertical of the temporal fossa?. FrOntals visible above as erect triangular 

 or retrorsely falciform wedges between the maxillaries and supraoccipital. 

 (Physeteroidea. ) 



PHYSETERIDAE. (LXX.) 



II. Rostrum of skull prolonged into a slender, straight beak, the inter- 

 maxillary and maxillary bones forming a cylinder, bearing teeth on its 

 proximal portion. (Rhabdosteoidea.') 



RHABDOSTEIDAE. (LXXI.) 



SUPER-FAMILY DELPHINOIDEA. 

 LXVI. INIIDAE. 



Genus. 



Inia D'Orb. 



Tretosphys Cope. 

 Zarhachis Cope. 

 Priscodelphinus Leidy. 

 Ixacanthus Cope. 

 Lophocetus Cope. 



Extinct Inildaet 



