NATURAL SCIENCES OF PHILADELPHIA. 167 
Fig. 7. nels are probably worn by the greatly de- 
PE veloped central tooth of the lingual membrane. 
an I do not agree with Morse in considering the 
Jaw of Z. milium. 
[Morse.] great development of the central tooth, and 
the channels on the jaw as generic characters. 
Z. Binneyanus is described by Morse with 60 rows of 283 —1—23 
teeth, with two perfect laterals which have a form of inner side 
cutting point. 
On pl. XVIL., fig. 13, I give a figure of the teeth on a membrane 
examined by me, kindly furnished by Mr. Anson Allen, of Orono, 
Maine. I find 19—1—19 teeth, with 3 laterals. I doubt there being 
any inner cutting points to the lateral teeth. | 
4. ferreus (pl. XVII., fig. 9), is described by Morse with 39 
rows of 20—1—20 teeth. I 
Fig. 8. found 20—1—20 teeth also, 
with 2 laterals. The cen- 
tral tooth is greatly de- 
veloped, and the jaw (fig. 
8) has vertical median 
channels, or groves, as in 
Z.milium (see above, fig. 7). 
- Jaw of Z. ferreus. [Morse.] 
4. conspectus, not examined. 
4. exiguus. I give here a copy of Morse’s figure, having 69 
Fig. 9. 
Z, exiguus. 
rows of 16—1—16 teeth, with 4 perfect laterals. The transition 
teeth and several of the adjoining marginals are described by 
Morse with a small side spur to their cusps, apparently of the 
same type as I have figured for Macrocyclis Vancouverensis (pl. 
I., fig. 4). On pl. XVII., p. 14,1 give a drawing of a specimen 
examined by me. I found 16—1—16 teeth with 5 laterals. 
Z. chersinellus, not examined. 
