ACTINIARIA 



species has namely proved that the weak basilar muscles, which I supposed to be present, are not such muscles 

 but the undermost part of the parietal muscles. The conclusion in my preliminary report of this genus that 

 it was provided with basilar muscles, was somewhat hastily drawn, as the one species was flattened in the 

 basal end and the other one, the contracted column of which was very low, was with a very broad base attached 

 to a shell. This species thus has the power to considerably alter its basal end from rounded physa-like to a 

 flattened wide basal plate , as it is also the case with Cactosoma and Milne-Edwardsia carnea (compare these 

 forms). Thus the only criterion, if a genus is provided with a real pedal disc, is the presence of real basilar muscles. 



Ophiodiscus (type 0. annulatus- R. Hertw.). This genus agrees with Sicyonis in the presence of con- 

 siderably fewer tentacles than mesenteries, in the structure of the tentacles and of the oral disc, and 

 in the differentiation of the mesenteries into sterile, filament-bearing and fertile, filament-loose mesenteries. 

 Hertwig, however, (1882) does not mention a different development of both mesenteries of the same pair, 

 which is possibly due to his having overlooked it, as the specimen was badly preserved. This is rather im- 

 portant, as Hertwig probably has also overlooked the same case in Sicyonis crassa. The only obstacle put 

 in the way of a conjunction of Ophiodiscus and Sicyonis, would be, that the tentacles of Ophiodiscus are 

 arranged in a cycle and that they are very long. It ought, however, to be observed that the tentacles were 

 for the greater part torn off and that only bad fragments of them remained. Hertwig's figure of the exterior 

 of Ophiodiscus is also very reconstructed. For my part I think that no conclusion, as to the real length of 

 the tentacles, can be drawn on basis of the presence of the long tentacle-thread, as I have observed how 

 very much prolonged perfectly slack tentacles of several Actinians can be. Finally, as to the supposed pre- 

 sence of pseudo-tentacles in Ophiodiscus annulatus, it has not been proved that the single pseudo-tentacle 

 observed belongs to the animal 1 . Neither has Hertwig dared to add it to the genus nor to the species char- 

 acters (compare also Simon 1892 p. 9). The presence of pseudo-tentacles in a deep-sea form is also very 

 unlikely. On basis of the named cases I think that Ophiodiscus is identical with Sicyonis or at least nearly 

 allied to it. Several authors as Me. Murrich have referred Ophiodiscus to the family Lebruniidae. In reality 

 this genus has nothing to do with Lebrunia, the structure of which is quite another. 



Paractinia (type P. striata (Riss.). During a visit in Turin 1899 Professor Rosa presented me with 

 2 specimens which he had seen living, and determined as this species. The exterior of both specimens agrees 

 well with the description by Andres, and there were no acrorhagi. An examination of the sphincter showed 

 that it was well developed diffuse, but endodermal and different from that of Actinia. As no reproductive 

 organs were developed its definite position is somewhat uncertain, but I think that Paractinia is the same 

 genus as Gyrostoma. 



Paractis type? It is questionable, which species of Paractis, enumerated by Milne-Edwards, may 

 be regarded as the type. Only when this has been determined, we may proceed to characterize the genus. 



Paranthus (type P. chromatoderus) (Schm.) and Parantheoides (type P. crassa Carlgr.). I have shortly 

 characterized these genera (1898 p. 27). Concerning Paranthus I have shown, on basis of an examination of 

 the type and of a species from N. America, that at least 12 pairs of mesenteries are perfect and that the re- 

 productive organs arise already on the mesenteries of the first cycle. In opposition to this, Maguire (1898 

 1 Stephenson (1920 p. 56o--s6i) is of the same opinion. 





