FRESH-WATER FISHES OF SIAM, OR THAILAND 407 



The ovaries undergo bilateral development and the eggs attain a 

 large size before extrusion. The number of eggs produced by a single 

 fish is relatively small, probably never exceeding 100 at one time in* 

 any local species. As they may be from 1 to 1.5 cm. in diameter when 

 ripe, very little space is left in the abdominal cavity for liver, stomach, 

 intestines, and other organs, all of which undergo shrinkage or tem- 

 porary atrophy, and in the later stage of the ovarian development di- 

 gestion is necessarily suspended, with the intestines reduced to mere 

 strings and the passage of food physically impossible. 



The most important characters for separating the species are the 

 teeth. Such characters, especially those of the palatine teeth, have 

 been used largely in the preparation of the key, which has been adapted 

 from Weber and de Beaufort's excellent presentation. 



la. Palatine teeth in one group on each side. 

 2a. Patches of palatine teeth ovoid or elliptical. 



3a. Palatine teeth coarsely granular or molarlike in large suboval parallel 

 patches. 

 4a. Band of teeth in upper jaw 6 to 8 times as long as broad and not 

 medianly constricted. 

 oa. Palatine teeth placed far back, separated from jaw teeth by a space 



nearly equal to length of patch ; dorsal spine stout maculatus 



56. Palatine teeth placed well forward, separated from jaw teeth by a 

 space equal to width of patch ; dorsal spine moderately 



stout gagora 



46. Band of teeth in upper jaw 3 times as long as broad and medianly 



constricted : dorsal spine very slender sciurus 



36. Palatine teeth villiform or sharply conical. 



6a. Palatine teeth in small oval patches, smaller than eye, their long 

 axis oblique, separated from each other by a space 2 or 3 times 



their least diameter truncatus 



66. Palatine teeth in transverse ovoid or elliptical patches about 2 times 

 as long as broad, separated from each other by a space about equal 



to their least diameter macronotacanthus 



26. Patches of palatine teeth roughly triangular. 



7c. Band of teeth in upper jaw long, narrow, arcuate, 8 to 10 times as long 

 as broad ; anterior side of palatine patch longest, rounded, and sepa- 

 rated from its fellow and from jaw teeth by a space somewhat less 

 than breadth of band ; head shields granular ; dorsal spine very long 

 and strong, granulated on anterior surface, equal to or longer than 



head caelatus 



76. Band of teeth in upper jaw 4 to 5 times as long as broad ; patches of 

 palatine teeth large, compact, separated from each other and from 

 jaw teeth by a space about one-third breadth of jaw band ; head 

 shields mostly smooth; dorsal spine weaker, less granulated, shorter 



than head venosus 



16. Palatine teeth in 2 groups on each side. 



8a. Patches of palatine teeth in antero-posterior series; teeth granular. 

 9a. Anterior patch of palatine teeth consisting of a few gi-anular ele- 

 ments, sometimes altogether wanting, far separated from jaw teeth 

 and from posterior patch, which is large, oval, with its long axis 

 inclined outward ; sides of occipital process straight, argyropleuron 



