ERENNA REVISION 
tentillum . .. reminds one at once of the tentilla described by 
BEDOT’. They concluded (p.69) that ‘there exists undeniably the 
closest relationship between the tentacles and tentilla of Erenna 
Richardi and Erenna Bedoti.’ So why did they separate them? Their 
earlier logic (p. 66) “We therefore called this only specimen Erenna, 
using a new species denomination “Bedoti” as of course we cannot 
decide whether the tentacles described by BEDOT belonged to a 
specimen entirely identical with ours’ seems very obscure. 
Lens and van Riemsdijk suggested a possible difference between 
the tentilla of their specimen and that of Bedot. They believed that, 
in the largest tentillum, the free end of the cnidoband was proximal 
(‘basal’) while in Erenna richardi it was distal (although they 
referred to the latter as ‘proximal’). They also noted the presence of 
a small black spot in the distal region of the cnidoband, which they 
suggested would become the ‘ocelli’ that Bedot described. How- 
ever, the ‘ocelli’ of E. richardi are positioned toward the end of the 
terminal process, even in the developing tentilla (see Fig. 6C, D). 
Have, then, Lens and van Riemsdijk misinterpreted the structure of 
their tentilla? Close examination of their illustration (Plate XI, fig. 
89) suggests that this is probable. It is suggested that what they call 
the pedicle is, in actuality, a very deformed terminal process; while 
the ‘apical part’ (terminal process) is the pedicle. Then the free end 
of the cnidoband is distal, as it is in E. richardi. For this to be so, the 
spot, which lay close to the proximal end of the cnidoband, and 
which they thought was equivalent to the ‘ocellus’ of E. richardi, 
must be considered an artefact, and that the true ‘ocelli’ have been 
destroyed. This is borne out by Lens and van Riemsdijk (1908, p. 69) 
statement that ‘Microscopical sections have been made but the 
material is unfortunately absolutely insufficient, the different layers 
being all destroyed’. It appears that all the largest tentilla were 
sectioned as none are now present with the type material. However, 
some developing tentilla are still present with the holotype and these 
conform exactly with those of E. richardi. Thus, there does not 
appear to be any concrete evidence to separate specifically Lens and 
van Riemsdijk’s material from that of Bedot. 
This conclusion was reached by Totton (1965), who considered 
Erenna bedoti to be conspecific with E. richardi. However, 
Margulis (1977, 1990) resurrected the debate, when she described 
another specimen of E. richardi Margulis (1997). She correctly 
noted that, on the nectophores, there were two digitate processes 
on the ventral side of the thrust block, and 2—3 extra ridges on the 
lower lateral facet. On the siphosome she found, as indeed had 
Lens and van Riemsdijk (1908), the presence of peculiar muscular 
outgrowths, but did not know their function. They are, undoubt- 
edly, the remains of the muscular lamellae to which bracts were 
once attached. One curious feature she described was that one 
detached tentacle arose from a black-pigmented formation that 
had a spherical dilation on each side. This was, of course, the 
basigaster of the gastrozooid, but she failed to appreciate this. The 
youngest tentillum had a digitate outgrowth in the region that was 
to become the cnidoband; the oldest were as Bedot (1904) 
described them. Margulis (1977) then made a brief comparison 
with Lens and van Riemsdijk’s (1908) description of E. bedoti. 
The only differences she noted were that the tentacles of E. bedoti 
lacked the basal outgrowths (i.e. the basigaster), and that their 
young tentilla did not have a digitate outgrowth. 
These points were addressed further by Margulis (1990), when 
she described fragments of another specimen that she referred to 
Erenna bedoti. The key features by which she distinguished this 
specimen from E. richardi were that:- 
a) the thrust block on the nectophore was smaller, with its distal 
margins stretched into thread-like outgrowths; and that the two 
175 
processes on its ventral surface were digitate or papillose, but not 
lamellate as in Erenna richardi; 
b) there were marked differences in the structure of the gastrozooid, 
and; 
c) the young tentilla of Erenna bedoti had an oval outgrowth, while 
in E. richardi it was finger-shaped. 
As has been shown above, the size of both the thrust block and the 
digitate processes varies with the size of the nectophore of Erenna 
richardi, which, as will be seen, is the only erennid species to have 
such processes. Thus, judging from her illustrations, the damaged 
condition of Margulis’s material is the most likely explanation of the 
differences she noted. It should be noted, moreover, that black 
pigment was present in Margulis’s material. The differences in the 
gastrozooids mainly concern the basigaster. Margulis now recog- 
nised that, in Erenna richardi, this was the large structure, with two 
large rounded lobes, that she had found at the proximal end of the 
tentacle. However, such a structure was not found on the larger 
gastrozooids of her latest specimen; although it was clearly large and 
inflated on the younger ones. This would be a reasonable difference 
if Margulis had not given the impression that the basigaster had been 
destroyed, by describing how its outer coating began to shed until it 
was completely absent. Personal experience has shown that it is, 
indeed, easy to destroy the epidermal layers of the basigaster. 
Finally, the differences between the young tentilla are considered to 
be mere reflections of their state of growth. The important similari- 
ties between Margulis’s (1990) material and E. richardi are that in 
both there is a pair of protuberances on the ventral side of the thrust 
block of the nectophore, and that black pigmentation is present. The 
former, and almost certainly the latter, of these are characteristics for 
only E. richardi and, thus, it seems inconceivable that E. bedoti is 
nothing more than conspecific with E. richardi. 
Erenna laciniata sp.nov. 
HOLOTYPE. The specimen from JSL II Dive 1454 is designated 
holotype, and has been donated to the Natural History Museum, 
London where it is registered as BMNH 2000.1821. 
MATERIAL EXAMINED. The description is based on two specimens 
collected by the JSL II submersible during dives 1454 (30 viii 1987; 
24°30.8'N 83° 45.2'W; depth 811 m) and 1688 (11 x1988; 26°23.5'N 
78°39.5'W; depth 853 m). 
DIAGNOsIS. Nectophores large, dorso-ventrally flattened, with 
only basic ridge pattern; with weak division of apico-laterals close to 
ostium. Thrust block small, with U-shaped median indentation and 
ventral flaps, but no conical protuberances. Lateral radial canals 
only slight thickened at apico-lateral corners of nectosac. Bracts of 
two types, with lateral flap, more extensive in one type than the 
other. Tentilla characteristic, with terminal process arising close to 
base of cnidoband and bearing two distal ‘ocelli’. 
DESCRIPTION 
PNEUMATOPHORE. The pneumatophore measured c. 2.9 x 1.9mm; 
gas expansion having ruptured its base. There were no obvious 
striations or pigment. 
NECTOSOME. Each specimen had 50-60 nectophores, which, in 
life, were arranged biserially. 
NECTOPHORE. (Figs 8,9). Flattened, up to 25 mm in length, 29 mm 
in width and c. 5 mm in height. Large tapering axial wings. On the 
mature nectophores (Fig. 8) the thrust block was relatively small and 
divided into two parts by a median U-shaped indentation. 
