166 PROCEEDINGS OF THE ACADEMY OF 



Morse gives a similar figure. The European Z. viridulus as 

 figured by Lebmann (Z. purus) has a similar dentition ; be gives 

 23 1 23 teeth, with 3 laterals. 



There are decided side cups as well as cutting points to central 

 and lateral teeth. 



Z. indebitatus (pi. XVII., fig. 3). The lingual examined has 

 38 1 38 teeth, with 3 perfect laterals. Morse counted 53 rows 

 of 39 1 39 teeth, also three perfect laterals. 



Z. limatulus (pi. III., fig. 3)? has 23 1 23 with 5 laterals. 



Z. minusculus (pi. XXL, fig. 9). Morse's figure shows four 

 perfect laterals. He counted 52 rows of 12 1 12 teeth. It will 

 be noticed that his figure does not show the cutting points of the 

 side cups of the central and lateral teeth, which I have found in 

 specimens lately examined from Florida. I found a similar num- 

 ber of teeth. 



Z. milium is described by Morse (fig. 6), as having 68 rows, of 

 17 1 17 teeth, with only 2 perfect laterals. The next six teeth 



Fig. 6. 



Z. milium. 



are shown to be bifid, not only the one or two transition teeth, 

 but the decided marginals. I have also drawn the membrane of 

 this species (pi. XVII., fig. 8). I found 18118 teeth, with 3 

 laterals. 



The peculiarity of the lingual of this species is the great de- 

 velopment of the central tooth. The jaw also is peculiar in having 

 vertical channels worn upon its anterior surface, extending down 

 to the cutting margin (see fig. 7, copied from Morse). These chan- 



