SYSTEMATIC SURVEY—SCYPHOMEDUSA. 173 
and are divided into two groups, Trachomeduse and Narcomeduse, 
according to the position of the gonads. The fresh-water medusz 
Limnocodium and Limno-- 
cntda may possibly belong by? 
to this group. \\y f far 
Geryonia, Carmarina, - Pies 
Ey] 
Cunina, Aeginopsis. 
2. Order Siphonophora. 
—Free-swimming colonies 
of modified medusoid per- 
sons (medusomes), with 
much division of labour. 
Physalia _ (Portuguese 
man-of-war), Dephyes, Vel- 
ella, Porpita. 
Incerte ‘sedis. Grapto- 
lites.—Extinct unattached 
colonies with a rod-like 
axis found in Upper 
Cambrian, Ordovician, and 
Silurian systems, The 
colony is usually linear, 
and consists of cup-shaped 
hydrothecze borne on one, 
two, or four sides of the 
solid axis (wz~gula). Each 
opens into a common 
median canal. At the 
proximal free end there 
is a- minute triangular 
or dagger-shaped body 
—the szcu/a—which re- 
presents the embryonic 
skeleton. Some repro- 
ductive bodies or gon- 
angia have been found. 
-The animals were prob- 
Fic. 90.—Campanularian Hydroid.— 
After Allman. 
ably free-swimming in #H., Hydrotheca or polyp-cup; AY; hy- 
muddy seas, and of a dranth, or polyp-head; G., gonotheca, 
Hyd. d 0 enclosing a reproductive polyp producing 
ydromedusan nature, medusoid buds; J/., a liberated medu- 
soid ; S7., basal stolon. 
Class II. ScypHoMEDUS (= Acraspeda) 
Jelly-fish with gastric filaments, sub-genital pits, and no velum— 
(1) Lucernarize.—Sedentary forms. Lucernaria, Haliclystus, and 
Depastrum. 
(2) Discomedusee.—Active forms, often with complicated life 
history. Aurelia, Pelagia, Cyanea, Rhizostoma. 
