$ 53. THE ACALEPHAE. 59 
ORDER II. DISCOPHORA. 
They have a simple centyal stomach, and move by means of discoid or 
campanulate contractions of their body. 
Famity: AEQUORINA. 
Genera: Aeguorea, Polyxenia. 
Famity: OcEANrIDaz, 
Genera: Oceania, Cytaeis, Thaumantias. 
Famity: GERYONIDAE. 
Genus: Geryonia. 
Famity: Ratzosrom1paz. 
Genera: Cephea, Cassiopea, Rhizostomum. 
Famity: MeEpvusrpar. 
Genera: Pelagia, Cyanea, Chrysaora, Medusa, Aurelia, Ephyra, Stheno- 
nia. 
ORDER HI. CTENOPHORA. 
Their mouth and stomach is simple and central, and they move by means 
of cilia arranged in longitudinal rows. 
Famity: Brrorpag. 
Genera: Beroé, Lesueuria, Medea. 
Famity: Mnemrapag, 
Genus: Eucharis. 
Famity: Ca.LrANrripag, 
Genera: Cydippe, Cestum. 
BIBLIOGRAPHY. 
Eschscholtz. _ System der Acalephen. Berlin, 1829. 
Lesson. Histoire naturelle des Zoophytes. Acaléphes. Paris, 1843. 
Wil. Horae tergestinae oder Beschreibung und Anatomie der im 
Herbste, 1843, bei Triest, beobachteten Acalephen. Leipzig, 1844. 
Ehrenberg. Ueber die Acalephen des rothen Meeres und den Organis- 
mus der Medusen der Ostsee, in the Abhandlungen der Berl. Akad. 1835. 
Mertens. Beobachtungen und Untersuchungen tiber die beroéartigen 
Acalephen, in the Mémoires de Académie des Sciences de St. Peters- 
burg, 6me series, Tom. IT. 1833, p. 479. Also, in Isis, 1836, p. 311. 
Brandt. Ausfirliche Beschreibung der von C. H. Mertens auf seiner 
Weltumsegelung beobachteten Schirmquallen, nebst.allgemeinen Bemerkung- 
