462 MOLLUSCA SUB-KINGDOM VI 
attended with great difficulty, since they frequently possess nearly identical characters 
in common, differing mainly in the operculum, which is not preserved fossil. 
B 

Fia. 894. 
He sha Le ; : 1G. 895. 
Fie. 893. A, Natica millepunctata, Lam. Plio- Fic 2 
Sigaretus haliotoideus, cene; Monte Mario, near Rome. J, Natica (Ampullina) patula, 
Linn. sp. Miocene; Operculum of N. multipunctata, 8. Lam. Caleaire Grossier ; 
Grund, Hungary. Woodw. Crag; Sutton. Damery, near Epernay. 
Sigaretus, Lam. (Fig. 893). Shell depressed, auriform, spirally striated or furrowed. 
Spire very low, with rapidly widening whorls. Aperture greatly 
distended ; operculum horny. Tertiary and Recent. 
Natica, Lam. (Figs. 894-897). Globose, semi-globose, ovate or 
pyramidal, smooth and lustrous, rarely spirally striated, umbilicate 
or not. The umbilicus, when present, often 
partially or entirely filled with callus. 
Aperture semi-circular or oval. Outer lip 
sharp; inneriap 
thickened by a callus. 
Excessively abundant 
from the Trias onward. 

Sub-genera: Ampul- 
lina, Lam. (Fig. 895); 
Amauropsis, Morch (Figs. 
896, 897); Amaura, MOll.; 
Innatia, Cernina, Gray ; 
Fic. 896. 
. 1G. S97. Ma. St 
Natica (Amaur- Fig. 897 Fic, Sys. 
opsis) Willemeti, Natica (Amauropsis) bul- Deshayesia — cochlearia, = sia . 3 
Lam. Calcaire biformis, Sowb. Upper Brongt. sp. Oligocene ; Neverita, Risso ; Mamilla, 
Grossier ; Damery, Cretaceous; St. Gilgen Monte Grumi, near Schum., ete. 
near Epernay. on Wolfgangsee, Austria. Vicenza. 

Deshayesia, Raul. 
(Fig. 898). Like Natica, but inner lip with thick callus and denticulated. Miocene 
and Pliocene. 
Family 6. Xenophoridae. Deshayes. 
Shell turbinate, without nacreous layer ; whorls flat, often covered with agglutinated 
foreign bodies. Base conical or flat, with a sharp peripheral keel. 
Aperture obliquely quadrilateral. Operculum horny. Silurian 
to Recent. 
The Xenophoridae are an ancient family, the modern re- 
presentatives of which have acquired a high differentiation. 
The radula is like that of the Oapulidae, Littorinidae, and 
Strombidae, not like that of the Trochidae. The earlier forms, 
encountered in the Silurian, present a great superficial re- Fic. 899. 
semblance to the Palaeozoic Trochus species. Xenophora heliacus, d’Orb. 
Eotrochus, Whitf. (Fig. 899). Thin-shelled, turbinate, widely Titan toast pea he's 
umbilicate. Whorls flat, rarely with agglutinated foreign particles. 
Base concave, its periphery formed by a compressed lamellar belt. Silurian to Recent. 

