RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 11 



II. — A CONTRIBUTION TO OUR KNOWLEDGE OF THE SIGA- 

 LIONINAE. 

 BY Dr. R. HORST. (WITH TWO TFXTFIGURES). 



Though our knowledge of the Sigalioninae much increased in the 

 last years thanks to the assiduous investigations of Mc Intosh, Pruvot et 

 Racovitza ! ), Darboux, Willey a. o., yet there still reigns a good deal of 

 confusion about the exact diagnosis of the genera. Sthenelais simplex 

 Ehl. 2 ) f. i. has rightly been ranged by Augener among the genus Lea- 

 nira 3 ) ; Leanira Giarcli Darb. 4 ) according to the investigations of Maren- 

 zeller belongs to Sthenelais 5 ) and Thalenessa stylolepis Willey G ) will prove, 

 as I presume, to be a species of Sigalion. Partly this may be ascribed 

 to the circumstance, that only a few of the investigators could dispose 

 of a large material and therefore must borrow their knowledge from the 

 often inadequate descriptions of others ; but it may also have been caused 

 thereby, that there was no agreement about the characters, that offer a 

 thrustworthy criterion for the distinction of the genera. However von 

 Marenzeller in his critical account of the genus Leanira 7 ) has given us 

 a clear review of the various often inexact ideas of the authors regarding 

 this matter and stated that besides the presence or absence of the ten- 

 tacle (median antenna) and the situation of the lateral antennae (on the 

 prostomium or on the buccal segment), the structure of the ventral 

 bristles furnish „das ausschlaggebende Moment", to distinguish the dif- 

 ferent genera 8 ). 



As the Siboga-expedition collected représentants of this group at no less 

 as 37 stations 9 ), I could dispose of a rather large material and I had 

 the opportunity to corroborate as well as to extend the investigations of 

 von Marenzeller. Not only I could examine several species of the genera 

 hitherto known, except one : Eusthenelais Mc Int. ; but I met with a 

 worm, dredged at Stat. 2 in Madoera-strait, that in my opinion belongs 



1) Faune des Annélides de Banyuls, Archiv. de Zoologie experiment. 3e Sér. Vol. 1J1, 1895, p. 339. 



2) Ehlers, Florida-Anneliden, 1887, p. 60. 



3) West-Indische Polychaeten, Pull. Museum Comp. Zool. Harvard College, Vol. 43, p. 91. 



4) Darboux, Recherches sur les Aphroditiens, Bull. Scient. France et Belgique, t. 33, 1900, p. 123. 



5) Polychâten des Grundes, 1902, p. 7; Fauvel, Polychètes Hirondelle et Princesse-Alice, p. 30. 



6) Ceylon Pearl-oyster Fisheries, IV, Polychaeta, 1905, p. 261. 



7) loc. cit. p. 8. 



8) Unfortunately a „lapsus calami" has crept into his account; for he says „ausserdem cha- 

 racterisirt Mc Intosh seine Gattung {Thalenessa) noch durch die Bemerkung, dass der unpaare 

 Stirnfiihler sehr kurz sei, dass zwei Antennen (unsere Fühler-wim perpolster) vorhanden 

 etc ," whereas the lateral antennae of Thalenessa have nothing to do with antennal ctenidia. 



9) A full account of these worms will be published in the Siboga-expeditie. Polychaeta errantia. 



