54 
The tentacles, which are inserted into the 
bell margin by endodermal bulbs, were quite 
contracted in most specimens; however, it 
was immediately apparent that the older ten- 
tacles are somewhat longer and larger than 
the younger ones. The tentacle bulbs are light 
yellow to cream in color and much more 
opaque than the tentacles. 
The shape and general appearance of the 
medusa is shown in Figure 2, although only 
one quadrant is shown with all its details. It 
will be noted that there are four interradial, 
subumbrellar pouches which extend the sub- 
umbrellar cavity well above the level of the 
stomach. This is a characteristic of all three 
of the species described in this paper. 
The nematocysts of the genus Prohoscidac- 
tyla are known for the hydroid in two in- 
stances (Russell, 1938 ; Hand and Hendrickson, 
1950) and in one case for the medusa (Hand 
and Hendrickson, 1950) and in this latter case 
only for very immature medusae. The nema- 
tocysts of adult P. flavicirrata were studied, 
and a simple cnidom of two types was found 
as follows: 
Cnidothylacies 
Macrobasic euryteles. . .22 — 30X9 — I4^t 
Desmonemes 5 — 7X4 — 6/i 
Fig. 2. Prohoscidactyla flavicirrata. a, Aboral view of 
the stomach; h, side view of stomach; c, whole medusa 
with only one quadrant shown in detail. 
PACIFIC SCIENCE, Vol. VIII, January, 1954 
Tentacles 
Macrobasic euryteles. .. 8 — 12X5 — l\x 
Desmonemes 5— 7X4— 6/i 
Figure 'ia-c illustrates the nematocysts. The 
desmoneme of the cnidothylacies appears to 
be identical to that of the tentacles. 
THE hydroid: Uchida and Okuda (1941) I 
have given a rather complete description of 
this hydroid, although a few additional re- 
marks and comparisons of their report with 
material from Puget Sound seems desirable. 
Several colonies of this hydroid were collected 
during the summer of 1950 in Puget Sound j 
by Dr. Ralph I. Smith of the University of I 
California at Berkeley and were given to the 
author for study. Detailed notes and sketches 
of the appearance and color of this hydroid 
in life were also gratefully received from Dr. 
Smith. 
The organization and arrangement of in- 
dividuals in P. flavicirrata are quite different 
from those of the other Pacific species. The 
gastrozooids and gonozooids stand in a dou- 
ble row or ring around the lips of sabellid 
tubes with the gastrozooids innermost, while 
the naked hydrorhizae tend to form parallel 
rows extending several millimeters along the 
long axis of the worm tube with occasional 
random anastomoses. The gonophores may 
arise either from the hydrorhiza near the base 
of an adjacent gastrozooid or actually from 
the proximal portion of the gastrozooid (Fig. 
Ah, c). What are presumed to be young or 
abortive gonozooids may occasionally be 
found at almost any point among the hy- 
drorhizae, although they were not as numer- 
ous as those found by Uchida and Okuda. 
Where young or new gonozooids are forming 
on the bases of the gastrozooids, the appear- 
ance is that the gastrozooid is growing a tail 
(Fig. Aa). Figure Ab illustrates the general 
appearance and organization of a colony. 
A total of 16 colonies was observed, and 
of these seven showed strongly parallel hy- 
drorhizal nets and the remaining nine varied 
from a reasonably close approach to parallel 
