§ 53. THE ACALEPHAE. 59 



ORDER II. DISCOPHORA. 



They have a simple central stomach, and move by means of discoid or 

 eampauulate contractions of their body. 



Family: Aequorina. 

 Genera : A&quorea, Polyxenia. 



Family : Oceanidae. 

 Genera : Oceania, Cytaeis, Thaumantias. 



Family : Geryonidae. 



Genus : Geryonia. 



Family : Rhizostomidae. 

 Genera : Cephea, Cassiopea, Rkizostomum. 



Family: Medusidae. 



Genera : Pelagia, Cyanea, Chrysaora, Medusa, Aurelia, Ephyra, Stheno- 



nia. 



ORDER in. CTENOPHORA. 



Their mouth and stomach is simple and central, and they move by means 



dinal rows. 



Family: Beroidae. 



of cilia arranged in longitudinal rows. 



. Genera : Bero'c, Lesueuria, Medea. 



Family : Mnemiadae. 

 Genus : Eucharis. 



Family : Callianiribae. 

 Genera : Cydippe, Cestum. 



BIBLIOGRAPHY. 



Esclischoltz. System der Acalephen. Berlin, 1829. 



LesRon. Histoire naturelle des Zoophytes. Acalephes. Paris, 1843. 



Will. Horae tergestinae oder Beschreibung und Anatomie der im 

 Herhste, 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 iiber die beroeartigen 

 Acalephen, in the Memoires de I'Academie des Sciences de St. Peters- 

 burg, 6me scries, Tom. II. 1833, p. 479. Also, in Isis, 1836, p. 311. 



Brandt. Ausfiirliche Beschreibung der von C. H. Mertens auf seiner 

 Weltumsegelung beobachteten Schirmquallen, nebst allgemeinen Bemerkung- 



