North American Species of Zonites, etc. 361 
of Mesodon, though somewhat lke a gigantic MW. Mitchelliana. 
The jaw has 16 ribs. 
The lingual membrane (pl. XIV, fig. F) is long and narrow : 
teeth 64-1-64, with about 15 ertone laterals on either side of 
the central line. The central and lateral teeth have no side cusps 
or cutting points, and only on the extreme marginals does a side 
cutting point appear. The cutting point of the marginals is long. 
Thus the dentition is hke that of clawsa and thyroides. 
The genitalia are figured on pl. XIV, fig. EK. ‘The genital 
bladder Gh b.) is large, oval, on a short, narrow duct: the penis- 
sac (p. Ss.) 18 long and stout, with a sub-central gonetratolion sauine 
prostate gland (pr.) is highly developed. 
Helix (Dorcasia?) slobulus, Mill. 
Cape Town, South Africa, Mr. J. 8. Gibbons. 
Jaw low, wide, scarcely arcuate, ends not acuminated: no 
anterior ribs. ; : 
Lingual membrane wide, with about 40-1-40 teeth. Laterals 
as well as centrals tricuspid. Pl. XIV, fig. K, gives a central, 
with its adjacent lateral and several inner marginal teeth. 
Both jaw and lingual membrane are quite different from those 
hitherto observed in Dorcasia, to which sub-genus Von Martens 
refers the species. 
Mr. Gibbons informs me that the eggs of this species are of 
very large size. It lives on sandy flats close to the sea margin, 
burying itself in the sand by day. 
Eielix (Pella) rariplicata, Benson. 
Cape Town, South Africa, Mr. J. 8. Gibbons. 
... jaw has ribs like those figured for Microphysa Lansingt. 
n Terr. Moll. U. 8., V,—i. e., flat, crowded, wide, numerous. 
“The hngual esr ORNS is long and narrow. ‘There are about 
16-1-16 teeth, with four laterals on either side of the central 
tooth. The central tooth has small detached side cusps and cut- 
ing points, as in Stropia, and the laterals are quite similar—a 
very unusual arrangement in the Helicide. ‘The marginals are 
low, wide, with one inner, oblique, wide bifid cutting point. 
The central, with its adjacent laterals and an inner marginal 
tooth, are given in pl. XIV, fig. H. 
