56 



VOLUTA.— OLIVA.— OVULA. 



AH have the aperture of the shell very narrow {fg. 



66), a disposition approaching to the characteristic of 



the following tribe. 



14. In the Tribe of Angiostoma, the aperture 



is generally so narrow that, to enter it, the foot of the 



animal is obliged to be doubled. 



In some, designated under the com- 

 mon name of Volutes — Voluta — the 

 aperture, which is of various forms, is 

 terminated by a notch without a canal, 

 and the columella is marked by oblique, 

 projecting plicfe (folds), {fig. 67) : they are sub- 

 divided into Volutes proper {fg. 56, page 5.2), 

 in which the aperture is wide, and the columella 

 is marked by some large plicse, and the last 

 whorl of the spire is sometimes ventricose, some- 

 times conical ; in the Mitra the spire is in 

 general pointed and elongated, and in Oliva, so 

 called from the oblong or ellipsoid form of the 

 shell, the aperture is long, narrow, and notched 

 opposite to the spire, and the columella is marked 

 by numerous plicae {fig. 67). 



16. In others the shell is oval, the spire is 

 concealed, and the aperture, which is long and 

 narrow, has no plicse on the side of the columella, 



but presents a notch or canal at its two extremities ; these are 



the OvuL^ (fg. 68). 



Fig. 67. 



OLIVA. 



Fig. 68. OVULA VOLVA. 



17, In others again, the Cythjeje (Porcelana), the shell, 

 which is protuberant in the middle, and almost as much con- 



14. What is the peculiarity of the tribe of Angiostoma? (Angiostoma, 

 Greek, aggeion, a vessel, and stoma, mouth.) 



15. What are the characters of Volu'ta ? (Voluta, Latin, a wreath.) 

 What is the character of Oli'va ? (Oliva, Latin, an olive.) 



16. What are the characters of the genus O'vula ? (Ovula, from the 

 Latin, ovum, an egg.) 



17. What are the characters of the genus Cyprse'a ? (Cypraea, Latin, 

 a cowry. 



