GASTEROPODA. 223 
which lives on the antipathes ericoides. When adult they attach 
themselves, singly or in groups, to the branches of the coral, or 
to each other, by a solid extension of the lips of the shell. The 
aperture becomes closed, with the exception of the respiratory 
canal. 
Monoceros, Lam. 
Etymology, monos, one; ceras, a horn. 
Synonyms, Acanthina, Fischer. Chorus, Gray. 
Type, M. imbricatum. Pl. VI., Fig. 4. (Buc. monoceros, 
Chemn.) 
Shell like purpura; with a spiral grooye 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. 
Distribution, 18 species. West coast of America. 
Fossil, Tertiary. Chili. 
M. giganteus (chorus) has the canal produced like fusus. M. 
cingulatum is a turbinella, and several species belong more pro- 
perly to lagena. 
PEDICULARIA, Swainson. 
Type, P. sicula. Pl. VI., Fig. 5. (Lhyreus, Phil.) 
Sheil very small, impet-iike; 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. 
Distribution, 1 species. Sicily, adhering to corals. Closely 
allied to purpura madreporarum, Sby. Chinese Sea. 
RICINULA, Lam. 
Etymology, diminutive of ricinus, the (fruit of the) castor-oil 
plant. 
Example, R. arachnoides. Pl. VI., Fig. 9 (= murex ricinus, L.). 
Shell thick, tuberculated, or spiny; aperture contracted by 
callous projections on the lips. Operculum as in purpura. 
Distribution, 34 species. India, China, Philippines, Australia, 
Pacific. 
_ Fossil, 3 species. Miocene—. Trance, 
PLANAXIS, Lam. 
pe, ©. enicata,. Pl. Vi., Fig. .6. 
Synonyms, Quoyia and Leucostoma. 
Shcll, turbinated ; aperture notched in front; mner lip callous, 
