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Genus Peponactis van Ben. 



Synonomy: Peponactis van Beneden, 1898. 



Cerianthidae whose larva? are almost spherical in shape, 'with short filiform marginal 

 tentacles, which are, in some species, rather late in developing. The median marginal tentacle 

 is similar to the others. The oral tentacles are small, enlarged at their extremity, and notably 

 inferior in number to the marginals. The siphonoglyph is moderately long; the directive 

 mesenteries are prolonged down the column for a considerable distance. 



5. Peponactis pilula n. sp. 



Stat. 37. Sailus Ketjil, Paternoster Islands. Plankton. 1 ex. 



Stat. 96. South-east side of Pearl Bank, Sulu Archipelago. Plankton. Numerous ex. 



Stat. 148. Lat. o°i7'.6S., long. i29°io'.5E. Halmahera Sea. Plankton. 1 ex. 



Stat. 186. Lat. 3 lo'.5 S., long. i27°2o'.5 E. North side of Manipa Strait. Plankton. 1 ex. 



The various examples from these different stations seem to belong to the same species, 

 which presents many differences from P. cequatorialis described by van Beneden (1898). 



In form all the specimens were practically spherical (PI. I, fig. 6) a slight flattening of 

 the oral pole being the only divergence from what would otherwise be a perfect sphere. A 

 slight elongated depression marks the centre of this flattened area. The examples from Station 

 96 were all transparent, allowing the attachments of the mesenteries to be perceived with 

 ereat clearness throuo-h the column wall, but this was clue to the ectoderm having been mac- 

 erated away over the greater portion of the column, portions of it persisting only in the neigh- 

 bourhood of the depression at the oral pole. In the examples from Station $7 more of the 

 ectoderm had been retained, and in those from Stations 148 and 186 it was entirely preserved, 

 the specimens being in consequence quite opaque and therefore in marked contrast to those 

 from Station 96. 



In P. czquatorialis van Beneden noted . the occurrence of both oral and marginal 

 tentacles, both sets being minute and filiform. In P. pilula no traces of tentacles could be 

 observed either in surface views or in sections. The difference may be due to difference in 

 age, since although the individuals of the two species that were studied were of practically the 

 same size, nevertheless the individuals of P. czquatorialis were in a somewhat more advanced 

 stage so far as the development of the mesenteries was concerned. 



Dimensions. The majority of the examples measured from 3.0 to 3.5 mm. in 



diameter, that from Station 148, however, being somewhat smaller, its diameter measuring 

 only - mm. 



Coloüration. Most of the specimens were colourless throughout or else showed 



a yellowish tinge toward the oral pole. The example from Station 37 was, however, yellowish 

 throughout, but whether this was normal or due to discolouration after preservation cannot 

 be determined. 



Structure. — The series of sections prepared from the 2.0 mm. example was, 



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S1ROGA-EXPEDITIE XV Cl. 5 



