97 
Yas 
+t Extinct Physeteridae? 
Gibterocetus Leidy. 
Oniocetus Leidy. * 
SUPER-FAMILY? RHABDOSTEOIDEA, 
LXXI. RHABDOSTEIDAE. 
> 
Extinct genus. 
Rhabdosteus Cope. 
MYSTICETE. 
[. 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 vertebra in whole or in 
_ part separated. Manus 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 vertebre coalesced. 
Manus broad, with five digits. (Flower.) 
BALAENIDAE. (LXXIII.) 
LXXII. BALAENOPTERIDAE. 
8UB-FAMILIES, 
I. Throat not plicated. Dorsal fin null. 
AGAPHELINAE, (A.) 
II. Throat longitudinally plicated. Dorsal fin developed. 
A. Frontal with the orbital processes much narrowed externally. (Flower.) 
Manus very long, with the four digits segmented into many phalanges. 
Dorsal fin hump-like. 
MEGAPTERINAE, (B.) 
B. Frontal processes with the orbital processes nearly as broad at the 
outer extremity as the base, or somewhat narrowed. (Flower.) Manus 
moderate, with the four digits having each not more than six phalanges. 
Dorsal fin high, erect, faleate or subfalcate. 
BALAENOPTERINAE. (0.) 
A, AGAPHELINAE. 
Agaphelus Cope. 
Rhachianectes Cope. 
February, 1872. 
ee 
