56 SYSTEMATIC PALEONTOLOGY 



which, being well marked in the fossil, ' is rounded off in the recent 

 specimen; the under and outer surfaces of the timpanic bone meet at 

 an acute angle/' Owen, 1846. 



In a summary of the species described [plate to face page xlvi] occurs 

 the statement that while the specimen has been described as Balaena 

 it is very probable that the ear bones belong with certain teeth that 

 the author has described as Balaenodon. However, the name Balaena 

 is the one used and it has been shown that the teeth and ear bones do not 

 go together. 



This is one of the most common of the Miocene Mysticocetes and 

 has a very general distribution. 



Occurrence. — Chesapeake Group. Maryland. 



Collection. — Johns Hopkins University. 



Cetacean ( ?) 

 Plate XXIV, Figs. 3a, 3b. 



A natural cast in sandy marl, shows the shape of the brain cavity of 

 some small member of the group. The general characters are shown 

 in the figures. 



Occurrence. — Chesapeake Group. Maryland. 



Collection. — Johns Hopkins University. 



Order SIRENIA. 

 Family MANATIDAE. 



Genus TRICHECHUS Linne. 

 Teichechus giganteus (?) (De Kay). 



Plate XXVI, Fig. 1. 



Manatus sp. Harlan, 1835, Med. and Phys. Res. p. 385. 



Manatus giganteus DeKay, 1842, Nat. Hist. N. Y. Zoology, vol. i, p. 123. 



Description. — The latter of these references gives only the name and 

 the fact that the specimen was discovered . on the western shore of 

 Maryland. The original description mentions the presence of " a cervi- 

 cal and a caudal vertebra of a gigantic species of fossil Manatus; the 



