B. G. Wilder on a fetal Manatee and Cetacean. 107 
A fetal Cetacean.—Fig. 6 represents, of natural size, a foetal 
cetacean kindly loaned by Mr. Alex. Agassiz, Curator of the 
Museum of Comparative Zodlogy. 
The specimen is labelled 7alcahuano, Chili, and was given to 
the late Prof. Agassiz upon the Hassler expedition. The donor, 
an old whaler, said it was from the “ Hump-back whale,” 
(Megaptera). But, aside from its small size, the blow-hole is a 
single transverse aperture as in Delphinide ; so that unless we 
assume that a transformation could occur so as to divide this 
into two holes, longitudinally or obliquely placed, we must re- 
gard it as the embryo of a porpoise or dolphin. 
Meter. 
Length from vertex to root of tail opposite anus, (2°3 inches) -055 
Tip of muzzle to supposed location of auditory meatus... .- 015 
Auditory meatus to Opposite ans 2). s Gee “042, 
Srpusite Alito tip. of tail. fe -018 
Real length as if extended (2:9 inches) ---- 075 
The smallest cetacean foetus of which I have found record 
(Gervais, 4,323, pl. XVII) was (102 (about four inches) long; it 
18 assigned to the common dolphin, Delphinus delphis. The 
upper and lower jaw of equal length, while in the specimen 
here figured the lower projects about 001 beyond the upper. 
The blow-hole is a transverse aperture 004 long. Its lips are 
rounded and tumid, and the posterior has a distinct hinder 
border. The eyelids are closed. 
The tail is uarrow and lancet-shaped, with no trace of a 
rminal notch No trace of dorsal fin is apparent, but as the 
cuticle of the back is somewhat abraded by friction during 
Cuvier’s arrangement of them as ‘“‘ Herbivorous Cetacea. 
Yet the hiatus between the Ungulata and the adult manatee 
and dugong is so great as to lead to the general recognition of 
the latter as a distinct order, Sirenia (Brandt, 2 ere ; Murray, 
8, 196; Owen, 12, ii, 281 ; Huxley, 13, 887); and three recent 
authors, by a kind of taxonomic’ reversion, seem to be again 
forcibly aa with the striking outward resemblances of 
the adult Sirenia to the Cetacea. The late compiler of the 
Catalogue of Seals and Whales in the British Museum includes 
the manatee and dugong among the Cetacea; Gray, 15, 62. 
Heckel (14, 5: , 556) recognizes their affinities with the 
_ -Ungalata, but makes the Cetacea the descendants of the Sirenia. 
