GASTEEOPODA. 223 



wluch lives on the antipathes ericoides. Wlien adult they attach 

 themselves, singly or in groups, to the branches of the coral, or 

 CO each other, by a solid extension of the lips of the shell. The 

 aperture becomes closed, with the exception of the respiratory 

 canal. 



MoxocEROS, Lam. 



Etymology, monos, one ; ce7xis, a horn. 



Synonyms, Acanthina, Fischer. Chorus, Gra5^ 



Type, M. imbricatum. PI. YI., Fig. 4. (Buc. monoceros, 

 Chemn.) 



Shell like purpura ; with a spiral groove on the whorls, end- 

 ing in a prominent spine on the outer lip. This genus is retained 

 on account of its geographical curiosity ; it consists of species 

 of purpura, lagena, turbinella, pseudoliva, &c. 



Distrihution, 18 species. West coast of America. 



Fossil, Tertiary. Chili. 



M. giganteus (chorus) has the canal produced like fusiis. M. 

 cingulatum is a turhinella, and several species belong more pro- 

 perly to lagena. 



Pediculaeia, Swainson. 



Type, P. sicula. PI. YI., Fig. 5. {Thyreus, Phil.) 



Shell very small, limpet -like ; with a large aperture, channelled 



in front, and a minute, lateral spire. Lingual dentition peculiar; 



teeth single, hooked, denticulated ; uncini, 3 ; 1 four-cusped, 2, 



3, elongated, three-spined. 

 Distrihution, 1 species. Sicily, adhering to corals. Closely 



allied to purpura madreporarum, Sby. Chinese Sea. 



EicrNTJLA, Lam. 



Etymology, diminutive of ricinus, the (fruit of the) castor-oil 

 plant. 



Example,'R. arachno'ides. PI. YI., Fig. 9 (= murex ricinus, L.). 



Shell thick, tuberculated, or spiny ; aperture contracted by 

 callous projections on the lips. Operculum as in purpura. 



Distrihution, 34 species. India, China, Philippines, Australia, 

 Pacific. 



Fossil, 3 species. Miocene — . France. 



Planaxis, Lam. 



Type, P. sulcata. PI. YI., Fig. 6. 

 Synonyms, Quoyia and Leucostoma. 

 Shelly turbinated ; aperture notched in front; inner lip callous. 



