254 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Tongue, Plates 12 and 13. 
The tongue of Rhinochimaera is larger than that of either of the other 
species dissected ; it is prominent, free from the floor of the mouth, and is well 
supported by a forward prolongation of the glossohyal cartilage. At the for- 
ward extremity it is truncate; the upper surfaces are covered with papillae, 
Plate 12. In both of the species of Chimaera dissected the tongue is seen to 
be much smaller, sharper in front, and to have much less of the glossohyal 
within it, Plate 13, Figures 1 and 2. The tongue of Callorhynchus callorhyn- 
chus, Plate 13, Figure 3, is greatly reduced or quite rudimentary, and the 
elossohyal is not produced into it as in the other forms described. From the 
shape of the tongue of Harriotta raleighana, it is evident that the glossohyal 
is produced into it; the skin of the organ is peculiarly thickened and folded on 
its upper surface, Plate 5, Figure 5, a consequence probably of rough contact 
and severe pressure by the hard portions of the food that has established the 
tritors on the teeth. The tongue of Harriotta is markedly different on the 
surface from that of either of the other genera, as is sufficiently obvious on 
comparison with the tongues figured on Plates 12 and 13, all of which are fur- 
nished with numerous papillae. 
Teeth, Plates 5, 6, 7. 
Tn all the known recent Chimaeroids the individual possesses three pairs of 
teeth, vomerines, palatines, and mandibulars, one pair of each; that is, two 
pairs of upper and one pair of lower teeth. Some of the fossil forms appear 
to have had a greater number, and some of the earliest of the extinct types 
apparently hada single pair of lower opposed to a single pair of upper teeth. 
Rhynchodus of the Corniferous and Hamilton limestones, Devonian, described 
by Newberry from Ohio, is said to be limited to the two pairs, vomerines and 
mandibulars, so also is Rhamphodus of Jaekel, from the Upper Devonian. 
These genera are of some interest in connection with this writing because their 
tooth-characters are in certain respects similar to those of Rhinochimaera, 
which among recent species possesses the most primitive features of dentition. 
Of living forms the resemblances in the outlines of the teeth are closer than in 
their details of structure. While the differences in these last are excessive, 
they are so distributed among the genera most closely allied in regard to other 
peculiarities as to prevent use in distinguishing higher groups. This is well 
illustrated by the teeth of Rhinochimaera and Harriotta, members of a single 
family, Plate 5, — instances respectively of the least differentiated and the most 
specialized in dental structures. An abundance of fossil Chimaeroid teeth sug- 
gests that they may have been shed at times by individuals as in Plagiostomia. 
While a periodical shedding of teeth might be expected from what obtains in 
other forms, we have as yet no evidence of its existence. The worn condition 
of the teeth in all specimens at hand points rather towar1 a continuous growth 
