836 The Siphonophores. [August, 
The anterior bell (a) is distinguished by some of the most im- 
portant characters of the genus. It is very small and hasa 
rhomboidal shape. The anterior end is not conical as in Diphyes 
nor rounded as in Galeolaria. 
The bell walls are stiff andthe 
bell cavity and bell opening 
relatively very small. Most of 
the interior of the bell is taken 
up by a large somatocyst of 
globular shape. The anterior 
and posterior bells fit closely 
together by faces, of which 
ff a that of the anterior is slightly 
\ a concave. ‘ 
+ Rar The posterior swimming- 
|- 8. bell (4) differs widely in shape 
$ BA, from that of either Diphyes 
Zh a Diphyes 
aea fI. or Galeolaria. Unlike the — 
! latter there are no circular 
z i) ene plates or rudders on the bell 
; margin. From the point of 
/ - union of anterior and posterior 
LA bells there passes from onè 
AN end of the nectocalyx to the 
ae eye other a number of serrated 
~ N ridges, five of which are con- 
k i tinued into triangular projec- 
l tions below the bell opening. 
MO Upon one side of the bell 
/ i between two of the pi a 
ca ; prominent of these parall io 
4 ib ridges there is a groove (e) for i 
pa the lodgment of the axis when 
Fic. 1.—Abyla pentagona (side view). his groove lies on 
a, anterior bell; 4, tiana an. ê, salah retracted. T 8 h sterior 
tudinal canal with cover; d, diphyizodid ; the same side of the po p 
s, Stem; 4, tentacle, swim ming-bell as the opening 
into the anterior bell cavity, Throughout a part of its length 
the anterior bell, for two-thirds of the distance to the terminati : 
this groove is covered by a thin transparent plate formed bwa 
reflexion of one of the neighboring longitudinal ridges. 
