FAMILY 10. PURPURIFERA. 215 
and external developments, as by the plait-like teeth, which Lamarck not 
unaptly terms false plaits. 
The shell of Ricinula may be described as being somewhat orbicular in 
form, and armed for the most part with sharp tubercles or spines, the 
spire being short, and sometimes a little depressed ; the aperture is longi- 
tudinal, and very narrow in the adult shell, in consequence of the colu- 
mella, which is smooth, arched, and terminated in an obliquely emar- 
ginated canal, being furnished, like the outer lip, with a number of small 
plait-like teeth. The operculum is horny, thin, and semilunar. 
Examples. 
P]. CCLVI. Fig. 1. 
Ricrnuta HorripA, Lamarck, Anim. sans vert., vol. vil. p. 231. Ency- 
clopédie Méthodique, pl. 395. f. 1. a, 6. 
Murex neritoideus, Gmelin. 
Purpura horrida, Duclos. Kiener. 
Pl. CCLVI. Fig. 2. 
RicinuLa Morus, Lamarck, Anim. sans vert., vol. vii. p. 232. Ency- 
clopédie Méthodique, pl. 395. f. 6. a, b. 
Purpura morus, Duclos. Kiener. 
Pl. CCLVI. Fig. 3 and 4. 
RicinuLa picitata, var., Lamarck, Anim. sans vert., vol. vil. p. 232. 
Encyclopédie Méthodique, pl. 395. f. 7. a, b. 
Ricinula lobata, De Blainville. 
Purpura lobata, Kiener. 
Pl. CCLVI. Fig. 5. 
RicINULA ARACHNOIDES (testa junior), Lamarck, Anim. sans vert., vol. vil. 
p. 232. Encyclopédie Méthodique, pl. 395. f. 3. a, 0. 
Purpura arachnoides, Duclos. [Kiener. 
