*22 
THE VOYAGE OF H.M.S. CHALLENGER. 
Campanularia chelonise, n. sp. (Pl. XI. figs. 2, 2a). 
Trophosome.— Hydrocaulus minute ; main stems springing at short intervals from a 
creeping stolon, and sending off from opposite sides alternate, rather distant ramuli, some 
of which send off secondary ramuli ; ramuli distinctly and regularly annulated either in 
their entire length or at their proximal and distal ends ; main stem similarly annulated 
just above the origin of every ramulus. Hydrothecse terminating the ramuli obconical, 
with even margin. 
Gonosome not present. 
Locality. — Found attached to the back of a Turtle, locality not recorded. 
This very minute, delicate, and graceful little species attains a height of about two- 
tenths of an inch, and is rendered remarkable by the deep, regular, and elegant annulation 
which occurs in its perfectly transparent chitinous perisarc at definite parts of the stem 
and ramuli. This annulation sometimes extends from the hydrotheca along the whole 
length of the supporting ramulus, while sometimes it occurs only at the distal and 
proximal ends of the ramuli, leaving a space free from annulation towards the middle. 
The main stem presents a group of similar annulations just above the points from which 
the ramuli are emitted. Many of the hydranths were well preserved in the specimen. 
Obelia, Peron and Lesueur. 
Obelia, Peron and Lesueur (the planoblast only), Char. gen. et sp. de Meduses, Ann. du Museum, 
t. xiv. p. 355, 1809. 
Generic Character. Tropliosome. — Hydrocaulus simple or branched, fascicled or 
monosiphonic. Hydrothecse campanuliform, destitute of operculum, pedunculate, with 
the cavity distinctly differentiated from that of the peduncle. 
Gonosome. — Gonophores medusiform vesiculate planoblasts with shallow umbrella, 
four radial canals on which the gonads are developed, short manubrium with four-lobed 
mouth, numerous rather rigid marginal tentacles whose roots are plunged into the 
substance of the umbrella, otocysts carried each close to the base of a tentacle, velum 
rudimental. 
The most important diagnostic characters of Obelia are found in its gonosome. The 
trophosome agrees in its essential features with that of other Campanularian Hydroids, — 
whether their gonophores be planoblasts or hedrioblasts — but the planoblasts of Obelia 
present characters so well marked as to render it impossible to confound these with the 
planoblasts of any other genus. 
Among these characters must be specially noted the shallow, almost discoid umbrella, 
the rudimental velum, the prolongation of the basal portion of the rather rigid marginal 
