In some genera there are no gills, e.g. Leaena.

[388]

These characters are not necessarily generic.

[389]

Eisig, "Die Capitelliden," Fauna u. Flora G. v. Neapel, Monogr. xvi. 1887.

[390]

Ed. Meyer., Arch. mikr. Anat. xxi. 1882, p. 769.

[391]

Vejdovsky, Denk. Akad. Wien, xliii. 1882, part 2, p. 33; and Rietsch, Ann. Sci. Nat. (Zool.) ser. 6, xiii. 1882, art. 5.

[392]