Ausfralidi^ Hydroids. 129 



Skutui.akia tknuis Bale. 



Serfiilan'a frnuis^ ]iale. Aust. Hydr. Zooph., 1884, p. 82, 

 pi. v., ti^a. i, 5, pi. xix., fig. 16; Jaderholm, Ark. f. 

 Zool.. k. svenska Vetenskapsakad. i., 1903, p. 287; 

 (?) Thornely, Rep't. to Gov't, of Ceylon on the Pearl 

 Oyster Fisheries of the Gulf of Manaar, Suppl. Rep't.. 

 viii.. 1904, p. 117, pi. ii. fi^r- 5. 

 Serfiihin'a gracilis (in part), Pictet, Rev. Suisse de Zool.,. 



i., 1893, p. 48. 

 Tlminrid tenuis, Borradaile. Fauna and Geogr. of tlie 



Maldive and Laccadive Archipel., ii., 1905, p. 841. 

 Sertidaria disfans (in part), Billard, Arch, de Zool. Exp. 

 et Gen., 4 ser., vii., 1907. p. 354; id., Exped. Sci. du- 

 Travailleur et du Talisman. Hydroides. viii., 1907, p. 

 187, figs., 10, 11. 

 Not Sertularia f/racili.s. Hassall, Hincks, Brit. Hyd. Zooph.,. 

 p. 262, pi. liii.. fig. 2; Nutting, Anier. Hydr.— Sert.,. 

 1904, p. 57,. pi. iii., fig. 10. 

 Not Sertularia distans. Allman. Gulf Stream Hydroids, 

 1877. p. 25. pi. xvi., figs 9, 10; Nutting (as S. pour- 

 talesi), Amer. Hydr. — Sert., 1904, p. 59. pi. v., fig. 5. 

 Not Bynamena distans, Lamouroux, Hist. Polyp. Cor.- 

 Flex.. 1816, p. 180. pi. v. fig. 1 a. b. 

 S. tenuis is mentioned here for the purpose of rectifying the- 

 synonymy, which has become confused owing to the association of 

 the species with some others, which, however similar in the form of 

 the hydrothecae. differ from it widely in other respects. Mark- 

 tanner-Turneretscher first suggested its identity with a European 

 form which he considered a variety of .S'. gracilis, and Pictet 

 definitely stated that the two species were identical, overlooking the 

 fact that the original description of S. tenuis was, in more than 

 one point, obviously incompatible with the known characters of 

 .S'. gracilis. In view of the same description it is difficult to imagine 

 why Borradaile referred the species to the genus Thuiaria. 



Billard accepted Pictet's statement, but having satisfied himself 

 from his examination of Lamouroux' types that the Bynamena 

 distans of that author was the same species as S. gracilis, ranked 

 all these forms together, as well as the S. distans of Allman, and 

 some other American species, which, however. Nutting considers 

 distinct. 



S. gracilis is a typical example of what Schneider calls the 

 " By n a mena-gr oup " of Sertularians ; that is to say, it has the- 



10 



