rh I, PROCEEDINGS OF THE ACADEMY OF 
PECTINIBRANCHIATA. 
Geomelania. Am. Journ. Conch., VII. 185, pl. xvii. fig. 7, 10. 
Blandiella reclusa, Guppy. Am. Journ. Conch., VII. 185, pl. xvii. 
fig. 5. 
Cyclotus stramineus, Rve. Am. Journ. Conch., I. 45, pl. v. fig. 1, 4. 
T. Bland. Jaw and teeth. 
Megalomastoma cylindraceum, Chemn. Am. Journ. Conch., I. 45, 
pl. v. fig. 2, jaw. TT. Bland. 
Megalomastoma Antillarum, Sowb. Same as last, fig. 3, teeth. T. 
Bland. 
Megalomastoma bituberculatum, Sowb. Am. Journ. Conch., VI. 
213, fig. 6. 
Tulotoma magnifica, Conrad. Ann. Lyc. N. H. of N. Y., 1X. 293, fig. 11. 
SCUTIBRANCHIATA. 
Stoastoma pisum, Ad. Am. Journ. Conch., VII. 184. | 
Helicina occulta, Say. Ann. Lyc. N. H. of N. Y., IX. 287, fig. 8.— 
Am. Journ. Conch., VII. 29, pl. ii. fig. 6. 
Helicina orbiculata, Say. Am. Journ. Conch., VI. 214, pl. ix. fig. 5. 
From the observations we have catalogued above, it appears that 
the jaw cannot be depended upon as a generic character in the 
genus Bulimus, as constituted in thesecond edition of Die Heliceen. 
We have found it strongly ribbed, with ribs as described below in 
Bulimulus, ribless, and ribless with a decided median projection 
to its cutting edge. In Limicolaria the jaw is described with ribs, 
we find it ribless in one species. In Bulimulus, von Martens 
describes the jaw as composite. We have shown it to be in one 
single piece, though divided by delicate ribs into numerous plate- 
like sections. The jaw is also very thin and transparent. This 
form of jaw seems constant in Bulamulus. It is also found in 
Cylindrella, Macroceramus, Amphibulima, Geotis, and even in 
Helix (H. turbiniformis). The tendency to an upper triangular 
median plate is more or less seen in this form of jaw—its greatest 
development being in Cylindrella. 
In the genus Helix as constituted by von Martens, the jaw is 
said to be ribbed, but we have found every variety of jaw except 
that with an upper additional plate, and that with free imbricated 
plates as in Orthalicus. We believe, however, that the form of 
jaw is constant in all the species of each section or subgenus of 
