546 CHORDATA. 
never replaces the functional teeth ; hence these latter are 
often regarded as the milk-teeth (f. Afetatheria). The homo- 
dont condition is correlated with the function of seizing and 
retaining small slippery fish which are not masticated but 
“ bolted ” entire, as in the case of sharks and other fish. The 
immense number of teeth is a great morphological difficulty, 
especially if we assume that the Cefacea are descended from 
terrestrial Eutheria, with teeth approximating in number 
Fig. 377.—DIAGRAMMATIC SECTION OF STOMACH OF PORPOISE. 
(After FLOWER and LYDDEKER.) 
h, Bile-duct. g, Duodenum. / Pylorus. ¢, Pyloric Portion. c, Middle 
Portion. 4, Cardiac Part. a, Gésophagus. 
to the typical dentition of 3343. It has been suggested 
that the tritubercular or multitubercular carnivorous type 
of tooth of these ancestors, losing its tearing and crushing 
function, became split up into three or more single-cusped 
elements which would give at least $4423 or 25. The 
rudimentary molar teeth of the ystacoceti or toothless 
whales are said to break up in this way into simple elements. 
