97 



Extinct Physeteridae? 



Orycterocetus Leidy. 

 Ontocetus Leidy. 



SUPEB-FAMILY ? KHABDOSTEOIDEA. 

 LXXI. RHABDOSTEIDAE. 



Extinct genus. 

 Rkabdosteut Cope. 



MTSTICETE. 



I. Skull with the maxillary region slightly arched, and with short baleen 

 plates. Rostrum broad at the base, gradually tapering, depressed. Front- 

 als with the orbital processes moderately prolonged, broad, and flat on the 

 upper surface. (Supramaxillary bones with the posterior margin deeply 

 excavated.) Tympanic bones elongated, ovoid. Lower jaw with the coro- 

 noid process more or less developed. Cervical vertebrae in whole or in 

 part separated. Manua narrow, with four digits (first wanting). (Flower. ) 



BALAENOPTERIDAE. (LXXII.) 



II. Skull with the maxillary region greatly arched, and with long, narrow 

 baleen plates. Rostrum narrow and compressed at the base. Frontals 

 with the orbital processes much prolonged, and extremely narrow and 

 rounded on the upper surface. (Supramaxillary bones with the posterior 

 margins entire.) Tympanic bones broad, rhomboid. Lower jaw with the 

 coronoid processes scarcely perceptible. Cervical vertebrae coalesced. 



Manus broad, with five digits. (Flower.) 



BALAENIDAE. (LXXIII.) 



LXXII. BALAENOPTERIDAE. 



SUB-FAMILIES. 



I. Throat not plicated. Dorsal fin null. 



AQAPHELZNAE. (A.) 



II. Throat longitudinally plicated. Dorsal fin developed. 



A. Frontal with the orbital processes much narrowed externally. (Flower. ) 

 Manus very long, with tha four digits segmented into many phalanges. 

 Dorsal fin hump-like. 



MEQAPTEB.INAE. (B.) 



B. Frontal processes with the orbital processes nearly as broad at the 

 outer extremity as the base, or somewhat narrowed. (Flower.) Manua 

 moderate, with the four digits having each not more than six phalanges. 

 Dorsal fin high, erect, falcate or subfalcate. 



BALAENOPTEB.INAJ5. (O.) 

 A. AQAPHELINAB. 



AgapJielus Cope. 

 Rhackianectes Cope. 

 February, 1872. 



