308 
C.C. Lu, A. Reid 
Figure 25 Sepia sulcata Hoyle; posterior end of 
cuttlebone, ventral view, female WAM 343- 
86, 65.1 mm ML, scale bar 4 mm, (IC - inner 
cone; OC - outer cone; S - spine). 
hectocotylised arm as biserial, but in all material 
examined in this study, these suckers are 
tetraserially arranged. The depth range occupied 
by this species is broad (404-150 m). There is some 
evidence to suggest that there might be a migration 
into relatively shallower waters for spawning. The 
largest males (65.9-67.6 mm ML), and females 
(85.7-96.2 mm ML) were collected at depths 
between 184-150 m (MV 56918, MV 56919, WAM 
3100-83), and all mature, while those collected at 
depths in excess of this range are smaller and 
include immature animals. 
This cuttlebone of this species shows some 
similarities with that of S. australis Quoy and 
Gaimard, 1832 from South Africa. In both species, 
the cuttlebone is narrow and oblong, distinctly 
pointed anteriorly, with pronounced dorsal median 
and lateral ribs and, on the ventral side, the lateral 
ribs in both species are bordered by grooves. The 
ventral grooves, and sulcus are much deeper and 
more pronounced in S. australis than in S. sulcata. 
Both species have the short, median ridge on the 
dorsal side of the cuttlebone, anterior to the spine. 
The posterior end of the cuttlebone is broader in S. 
sulcata; in S. australis outer cone is poorly 
developed and the inner cone is not raised forming 
a ledge. S. australis is darkly pigmented, unlike S. 
sulcata and has a distinctive unbroken longitudinal 
ridge at the base of the fins. The arm suckers in S. 
australis are arranged in four series, unlike those 
seen in this species. 
DISCUSSION 
With the inclusion of Sepia plana, S. senta and S. 
sulcata, 29 nominal sepiids are now known to occur 
in the Australian fishing zone (200 nautical miles 
from the coast). In addition to the three species 
described above, the following sepiids are found 
off northwestern Australia: Metasepia pfefferi 
(Hoyle, 1885); Sepia cottoni Adam, 1979; S. elliptica 
Hoyle, 1885; S. irvingi Meyer, 1909; S. latimanus 
Quoy and Gaimard, 1832; S. opipara (Iredale, 1926); 
S. papuensis Hoyle 1885; S. pharaonis Ehrenberg, 
1831; S. smithi Hoyle, 1885, and Sepiella weberi 
Adam, 1939. These latter species (with the 
exception of S. irvingi) are widely distributed in 
the Northern Australian Region, a zoogeographic 
zone recognised by Wilson and Allen (1987). This 
zone extends across northern Australia to southern 
Queensland. Though regions of overlap occur on 
each side of the continent, the predominantly 
tropical Northern Australian assemblage largely 
differs in species composition from the more 
temperate Southern Australian fauna. Most marine 
species within this region also occur elsewhere in 
the Indo-West Pacific, though many Australian 
endemics are found in the zone. Among the 
sepiids, S. cottoni, S. irvingi, S. opipara, S. plana, S. 
smithi, S. senta and M. pfefferi are known only from 
Australia at present. The presence of an animal 
very similar in appearance to S. senta in the 
Philippines, either a distinct species, or population, 
suggests that S. senta is unlikely to be a true 
Australian endemic. Sepia irvingi is classed by Lu 
(in press, a) as belonging to the Western Overlap 
zone. It is included in the list of species above as its 
distribution extends to the North West Shelf. 
Species in the genus Sepia are easily 
distinguished from the two other sepiid genera, 
Sepiella and Metasepia. Sepiella differ from other 
sepiids by the presence of a gland, and gland pore 
at the posterior end of the mantle between the fins, 
the mantle cartilage has a triangular tubercle, and 
the sepion has very short limbs. Metasepia can 
readily be recognised by the distinctive rhomboidal 
sepion which is situated in the anterior 2/3 - 3/4 
of the mantle (Khromov et. oL, in press). Table 10 
lists some characters which can be used distinguish 
representatives of the genus Sepia found off 
northwestern Australia. 
ACKNOWLEDGEMENTS 
We thank F. Naggs (BMNH), S. Slack-Smith 
(WAM) and V. Wadley (CS1RO) for providing 
specimens. For help with scanning electron 
microscopy we are grateful to F. Brink and D. 
Vowles at the E.M. Unit, Research School of 
Biological Sciences, Australian National University 
(ANU). Thanks also to M. Norman (Melbourne 
University), C. Rowley (Museum of Victoria) and J. 
Wilson (ANU) for assistance with photography 
and to A. Gibbs for providing work space and 
facilities at the Research School of Biological 
Sciences in Canberra (ANU) to Amanda Reid. This 
