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 ISIDiE. 



In the ' Challenger' report on the Alcyonaria, Professors Wright and Studer (14) 

 proposed a division of this family into three sub-families, Ceratoisidinse, Mopseinse and 

 Isidinse, 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 difl&culty 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 Ceratoisidinse and Mopseinse 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 Alcyonaria 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 II., 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 



