245 



is relieved by strongly marked transverse ribs. Both these species 

 are very common, and the latter is peculiar for its power of 

 ejecting a dark purple fluid when molested. The other representa- 

 tive of the family Ccccum trachea has a 

 shell something like that of Dentalium 

 (p. 238), being cylindrical and tubular, but it 

 differs in being closed at one end. 



In the succeeding 

 shells, of the family 

 Cerithiadce, the spire is 

 also considerably pro- 

 duced, so much so that 

 some of the species 

 closely resemble the 

 Turret shells, but they 

 are distinguished by 

 usually having an ex- 

 panded lip, at least in 

 the adult form ; and 

 the mouth is channelled 

 in front, and sometimes 



also behind. The animals of the group have short muzzles that 

 are not retractile, the tentacles are wide apart, and the eyes are 

 mounted on short pedicels. The median teeth are arranged in 

 a single row, with three laterals 

 on either side of each. 



Cerithium reticulatum re- 

 ceives its generic name from its 

 appearance to a small horn, and 



FIG. 173. SECTION 

 OF SHELL OP 

 Turritella 



Fin. 174. Turritella 

 communis AND 

 Ccecum trachea 



the specific name refers to the 

 netted appearance of its surface 

 due to the presence of numerous 

 little tubercles arranged in rows 

 a feature that serves to distin- 

 guish it from the small Turret 

 shells. It is a common shell, as 



is also the other representative of the family illustrated, but the 

 latter is rendered conspicuous by the enormously expanded lip that 

 has earned for it the popular name of Spout Shell. Its scientific 

 name is Aporrhais pes-pelicani, and the application of the specific- 

 term will be understood when the shell is viewed from above, for 



FIG. 175. Cerithium reticulatum 

 AND Aporrhais pes-pelicani 



