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IV. — On the Genus Porponia and Related Genera, Scottish National Antarctic 

 Expedition. By Professor Oskar Carlgren, Universitetets Zoologiska Institution, 

 Lund. Communicated by Dr W. S. Bruce. 



(MS. received August 12, 1913. Read January 19, 1914. Issued separately March 30, 1914.) 



[Plate IV.] 



In an Appendix to the Actiniae of the Challenger Expedition, P. Hertwig. 1882, 

 described a peculiar genus, Porponia, with two species, P. elongata and P. robusta, 

 which he characterises in the following manner: " Actiniarien (Hexactinien?) mit 2 

 Schlundrinnen ohne Ringmuskel, mit diinnwandigen Tentakeln, deren Basen auf der 

 ausseren Seite durch spangenformige Verlangerungen des Mauerblatts gestiitzt werden." 

 Partly owing to the badly preserved material, however, he did not venture to indicate 

 definitely its systematic position, though he considered it conceivable that it repre- 

 sented a transitional form between the Zoanthidse and the true Actiniae, or Hexactiniae. 

 Hertwig expresses the following opinion regarding the systematic position of the 

 genus : <; Die doppelreihige Stellung der Tentakel, die Abwesenheit vollstandiger 

 Geschlechtsepten (Macrosepten) und unvollstandiger, sterilen Septen (Microsepten) 

 sind Merkmale, welche an die Zoantheen erinnern, die Zahlen der Tentakel und der 

 Septen passen ebenfalls am meisten fiir diese Gruppe, da sie weder von dem Numerus 6 

 wie bei den Hexactinien noch von dem Numerus 4 wie bei den Paractinien bestimmt sind. 

 Auf der anderen Seite nahert sich die P. elongata durch den Besitz von zwei Schlund- 

 rinnen wieder mehr den Hexactinien, unter denen sie am meisten mit den Antheo- 

 morphiden ubereinstimmt. Ich halte es daher fiir sehr wahrscheinlich, dass P. elongata 

 eine Mittelform ist, welche den Ubergang von den Hexactinien zu den Zoantheen 

 bildet." Porponia possibly, he thinks, belongs to the Antheomorphidse, a family 

 supposed to be separated from the family Antheadse chiefly by the absence of a 

 sphincter and by the weak development of the musculature. 



Since R. Hertwig described this genus, it has not been made the subject of any 

 close examination, nor for this reason has its systematic position been discussed in 

 detail. Yet it is only right to mention that M'Murrich was inclined to refer the 

 genus Halcurias {Endoccelactis) to the neighbourhood of Porponia. " In fact," he 

 writes (p. 226, 1898), " I was inclined at first to associate it (Halcurias) with Porponia, 

 and was only deterred from doing so by the simplicity of the arrangement of the 

 mesenteries." (That Halcurias possesses a peculiar arrangement of the mesenteries, 

 which agrees with what I have described, 1897, for the genus Endoccelactis, was not 

 known to M'Murrich at that time.) 



A closer examination of the material which I received for investigation from the 



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