18 HELICOIDEA. 
GONOSPIRA, Swainson, 1840. (Gibbulina, Pfr., 1855.) Typical 
group. G. palanga, Fer. (xcii, 65). Isle of France. 
NEVILLIA, Martens. Whorls narrow, with strong perpendicular 
ribs. 3sp. Mauritius. G. clavulata, Lam. 
RaAveEnta, Crosse, 1873. 
Distr.—h. Blandi, Crosse (xcii, 66). Curacao. 
Shell allied to Spiraxis and Pupa, turreted, imperforate, sub- 
hyaline, columellar margin spirally twisted, outer margin bent 
inwards, and with a strong tooth in the middle. 
Famity HELICOIDEA. 
Shell heliciform, with usually depressed conical spire, and 
umbilicated ; outer lip simple. 
Animal differing from the true Helices by the absence of a jaw. 
Ruytipa, Albers, 1860. 
Distr.—31 sp. Australia, Tasmania, New Caledonia, ete. AR. 
bullacea, Pfr. (xcii, 67). Australia. 
Shell umbilicate, thin, convexly depressed ; undulately rugose 
or striate ; spire slichtly elevated ; whorls four or five, slightly 
flattened ; umbilicus wide and deep ; aperture oblong- ovate, 
sometimes dentate within; lip simple, acute, its extremities 
approaching. 
Viviparous. Teeth rather few, oblique, arcuated. 
DIPLOMPHALUS, Crosse and Fischer, 1873. Shell discoidal, 
planorbiform, spire depressed ; peristome simple, connected by 
a much-developed parietal callus. 13 species. New Caledonia, 
New Zealand, Australia. D. Megei, Lamb. (xciii, 68,69). N. Cale- 
donia. Differs from Rhytida by the very wide umbilicus and 
sunken excavation of the upper face of the shell; in the radula 
by the equal size of the lateral teeth. 
GUESTIERIA, Crosse, 1872. 
Distr.—G. Powisiana, Pfr. New Grenada. 
Shell imperforate, corneous, thin, depressed, quite involute, 
the last whorl only visible; aperture like that of Nautilus; peris- 
tome thin, simple. Animal unknown. 
Agrrore, Albers, 1860. 
Distr.—A. caffra, Fer. So. Africa. 
Shell: very thin, subglobose, costulately striate, with narrow 
umbilicus ; spire not prominent, obtuse ; whorls four, ventricose, 
strongly striated, the last descending at the aperture ; aperture 
large, semiovate; lip simple, acute; columellar margin widely 
reflected. 
Teeth very long, subulate, arranged in converging lines. 
