4 SYDNEY J. HICKSON. 
characterised by the presence of a certain number of four-rayed spicules of a type which 
does not occur in A. paessleri. On the whole then I am inclined to believe that 
A, paessleri is distinct from the other subantarctic species. 
FAMILY ISIDA. 
In the ‘Challenger’ report on the Aleyonaria, Professors Wright and Studer (14) 
proposed a division of this family into three sub-families, Ceratoisidinee, Mopseinee and 
Isidinze, based upon the shape of the spicules. The study of many specimens belonging 
to the family has convinced me that this sub-division is unnecessary and inconvenient. 
The many variations of spicule characters that are found in the species of a single genus 
render these structures unsatisfactory for the purpose of wide systematic differentiation. 
If we take a single species from each of two of the sub-families and compare them, the 
differences observed in the character and arrangement of the spicules may seem to 
be of a higher rank than the usual differences between genera; while, on the other 
hand, the examination of a large number of species of the same two genera will reveal 
so many intermediate conditions as to render the separation of the genera, on spicule 
characters alone, impossible. This kind of difficulty is particularly well seen in the 
case of the genera Ceratoisis and Primnoisis, which were placed by Professors Wright 
and Studer in the sub-families Ceratoisidinee and Mopseine respectively. In both these 
genera the branches arise from the calcareous internodes, a character which distinguishes 
them from the genera Acanella, Lepidisis and Isis belonging to the same family. The 
spicules in both genera are flattened and scale-like, but in the species attributed to 
Ceratoisis they are fusiform, whereas in those attributed to Primnoisis they are 
irregular flattened scales. In Ceratoisis, moreover, some of the spicules project as thorny 
processes from the calyx, whereas in Primnoisis they do not project. 
In the description of the Aleyonaria from the Cape of Good Hope (4) I described 
a new species under the name Ceratoisis ramosa, which has many characters resembling 
some of the species of the genus Primnoisis, but the species appeared to me to differ so 
markedly from Primnoisis in having the spicules on the tentacles arranged longitudinally 
instead of transversely that I concluded it must belong to the genus Ceratoisis. On 
re-examination of the specimens I have confirmed this observation, but may add to 
it the fact that many of these tentacular spicules project slightly from the surface. 
The examination of the Antarctic specimens brings additional evidence to show the 
inconvenience of separating the two genera. The specimen of Ceratoisis antarctica 
was found in the same locality as that of Ceratoisis spicata; the former undoubtedly 
belongs to the group of species hitherto called by the generic name Primnoisis, as 
none of the spicules project from the surface of the calyx; the latter, however, has 
very long spicules, many of which project as thorny spines. The projecting spicules 
of the calyx of Ceratoisis spicata, moreover, resemble those of C. grandiflora in having 
the base bifid (Cf. Plate IL, fig. 18a, with Prof. Studer’s (10) figure Taf. v., fig. 34b), 
but whereas those of C. grandiflora seem to be nearly smooth on the surface, those 
