104 - MOLLUSCA. 
Fam. OXYGNATHA. 
Jaw smooth, with a median projection at its cutting-edge. Median and lateral teeth 
of the radula subquadrate ; marginal teeth aculeiform. Shell ordinarily thin, glossy; 
edges of the aperture simple. 
For the purposes of this work, and to render easier the determination of the shells, 
I have excluded from this family all.the genera without external shell (Limacidse),: or 
with an incomplete one, partly covered by the soft parts of the animal (Vitrinide) ; 
and I propose to place them near the analogous forms of the Aulacognatha., 
OMPHALINA. 
Omphalina, Rafinesque, Enum, and account of some. remarkable Nat. Objects, p. 3 (Nov. 1831) 
(see Binney and Tryon, Complete Writings of Rafinesque, p. 67). 
Mesomphiz, Beck, Ind. Moll. p. 7 (1888). 
Subfam. Neozonitine, Pfeffer in Strebel’s Beitr. Mex. Land- und Siissw. Conch, iv. p. 1 (1880). 
Shell depressed, umbilicated, corneous, smooth and shining on the lower side; 
aperture moderately oblique ; peristome simple, thin. 
Foot with a double marginal furrow and a distinct mucous-pore at the hinder end. 
Edge of the mantle extending on the neck of the creeping animal, but not on the 
shell, Median tooth of the radula with a lateral cusp on each side; lateral teeth 
few (4-11), with the outside cusp only distinct and placed higher up; marginal teeth 
spiniform, numerous. Genital organs rather simple, without vesicule multifide or 
dart-sac. as ; 
For the anatomy, see Fischer and Crosse, Miss. Scient. Mex., Mollusca, i. pp. 143-151, 
t. 8; and Pfeffer, in Strebel’s Beitr. Mex. Land- und Siissw.-Conch. iv. pp. 1-4, 7, 9, 
12,17, t. 8, and t. 9. figg.1-8. Fischer and Crosse unite the Omphaline, the Palearctic 
Zonites, and the cosmopolitan Hyalinia into one genus, Zonites; Pfeffer makes it a 
distinct subfamily “ Neozonitine,” and splits it into three genera, Voreletia, Zonyalina, 
and Patulopsis. 
The shell is brown or yellow, unicolorous, or with one or, rarely, more dark spiral 
bands. The periphery is in most species rounded, even in young shells, in opposition 
to the Palearctic Zonites, in which the young shell is always, and the adult often, 
angulated. 
