332 



FAUNA ANTIQUA SIVALENSIS. 



In order to follow tlie relations of the teeth of Enlnjdriodov} 

 it is necessary to review the dental system of Lutra and 

 Enhycha. 



3+3 1+1 1 5+5 



3^; cat], y^^; mol. gvg; 



The formula in Lutra is : incis. 



18 



= ^ = 36. In the Enhydra (as shown in the solitary skuU 



preserved in the Museum of the Zoological Society) ; 

 3 + 3 . „„ 1 + 1. „_, 4 + 4 16 _oo The dental sys- 



incis. 



can. 



mol. 



= ii=32. 



2 + 2(!) ' ^""^' 1 + 1 ' " 5 + 5 ■ 



tem of the Otters is built very much on the plan of the 

 Martins (Fred. Cuvier, in ' Ossemens Fossiles,' art. ' Dentition 

 of the Carnassiers,' vol. iv.) with which it agrees numerically, 

 except in having a false molar less on either side of the 

 lower jaw. But in the signification of the teeth they differ 

 materially in the increased development of the tubercular of 

 the upper jaw, and in the greater degeneration, so to speak, 

 of the carnassier. The typical tubercle on the inside of the 

 latter, instead of being limited to a small knob connected 

 with the body by a narrow base, constitutes nearly half the 

 surface of the coronal, and is expanded into a wide disc, 

 bounded on its inner side by a sharp raised edge, occupying 

 the whole length of the inside of the tooth. The outline of 

 the carnassier is in consequence nearly triangular. The body 

 is still distinctly tricuspid, as in the higher Carnivora, but the 

 anterior cusp is reduced to little more than a well-marked 

 serrature or lobe of the basal ridge. The tubercular has a 

 development proportionate to that of the tubercle of the 

 carnassier. It is somewhat trapezoidal in the outline of its 

 coronal, which is oblong in the transverse direction, that is, 

 considerably broader than long ; it is divided lengthwise by 

 a deep hollow into two somewhat unequal halves, the outer 

 and smaller of which is subdivided by a shallow transverse 

 channel into two flatfish surfaces bounded by a raised edge ; 

 while the inner is expanded into a flat disc, bounded by an 

 edge, as in the tubercle of the carnassier, but it is of greater 

 extent and more complicated in form. This arises from the 

 anterior border of the coronal being raised up into a promi- 

 nent trenchant ridge divided into two denticles, and distinct 

 from the bounding basal ridge which sweeps round it. 



In the lower jaw the tubercidar is of comparatively small 

 size, nearly square, and its coronal is divided by a transverse 

 low ridge into two flattened nearly equal surfaces. The car- 

 nassier may be considered as made up of two parts, separated 



' So named from cfuSpi's the Greek 

 ■word for Otter, and oSovs. The 

 name has no sx^ecial reference to the 



modern Enhydra, which has a similar 

 derivation. 



