50 AMERICAN HYDROIDS. 



supplanted l>v l/iili-ciinn of Oken. 1 the species now included in the Lafoeida 1 in his genus Lnfix'ii; 

 many of the Campanularidse in L<i<>nil<-ti and (_'Iyt!<i. At nearly tho same time (INK!) Lamarck 

 issued the first edition of his classic work. Histoire naturelle des aniniaux sans vertebres, II, in 

 which he separated most of the present CampanularidsB under the name Campanularia, &ud the 

 Plumularidffi under the names Antenwula-ria and Pluntularia, and retained the name SertvUo/ria. 

 for the .species then known that would now be included in the family Sertularida-. In the .same 

 year, (ixlti), 2 Lainouroux published his Histoire des Polypiers coralligenes Flexibles, etc., in 

 which he diyided the sertularians into the genera J l <ixi/t/i,-<i^ which included the Pasytkea of sub- 

 sequent authors plus certain nonrelated forms, Di/nmnriKi, including the forms that would le 

 placed in Si'rt>d<ir!tt and Diji/mxi// in the present work, and Si I'tiilnrin, including forms with 

 alternate, hydrothecae, such as are now placed in Sertularella, Thuiaria, .[!>/< thi</ri<i, etc. 



The next work of importance is that of Fleming, 3 who instituted the genus Tlmnir'ni to 

 include what now would be called the typical species of that group. He followed Lamouroux in 

 the use of the generic name Dynamena. 



Johnston in his British Hydroid Zoophytes, 1X28, returns to the use of the genus Sci'tnlni-in 

 in nearly its original meaning, drops the genus J)yn<inu')M, and adopts the genus Thulnrin of 

 Fleming. 



In 1862 Louis Agassiz* differentiated the genus Diphoxin from the Sertularia. or Dynamena 

 of other writers, and uses the word SiTfitluriii in a very restricted sense, including only Scrtidn- 

 r'ni iii'i/< Htm. Tlniiiii'iii <-nj>ri xxiini, Aliii'fi/K/riii uli'ictnut^ and ^-1. jiJIi-ida. He also proposed the 

 genera Amphitrocha and C'otnlnm for certain species that are now included in Sertularelln, and 

 Amphisbetia for Sertularia op&rculata, 



With the great work of Hincks, British Hydroid Zoophytes, 1868, what may be called the 

 modern era began. He reinstated and modified the genus SertuLarella* which is b}^ far the 

 largest in the family, if not in the entire order Hydroida, and also proposed the genus JlydraR- 

 iiKinia for the S,/rfn1<ir!<i falcufa Linnaeus, which many writers had erroneously placed in the 

 Plumularidse. 



The further vicissitudes of the genus Sertularia arc sketched in preceding pages of the 

 present work, in connection with the general systematic discussion of the family. 



POINTS OF INTERCJKADATION BETWEEN SEKTULAKIA AND OTHER (iENEKA. 



As above defined, the genus Serfailaria is a well circumscribed group, but in certain indi- 

 vidual characters it has points of contact with other genera, among which the following may be 

 found in species treated in this work: 



fii-ftf. With T/n/iiiria, In several cases, such as S. f>/'xj>/n<<a, rlm/l, /n/< //', and dwinotd*'*, the 

 internodes are of irregular length and bear more than a single pair of hydrotheca?. In all such 

 cases, however, the hydrothecae are normally strictly opposite, and never subopposite nor subalter- 

 nate, as in Thuiaria. 



Si'cmiiL With Sert-idarella, in having a three-flapped operculum and three-toothed margin, 

 as in S. xi'i-titlui-loldw and -V. l>i-<-i-'n-ii<i1]nix. Here, also, the hydrothecje are strictly opposite and 

 Hot strictly alternate, as in X, rlnlnr. //</. 



T/i ifil. With Tit a !a r!u, in having a round aperture, without teeth, and an abcauline oper- 

 culum composed of a single flap as in .s'. <~l>-xi,,i>nl,t!. Here, also, the hydrotheca? are strictly 

 opposite. In this ease there is the further complication of extreme variability in the hydro- 

 thecal margin and operculum, there being an occasional hydrotheca in which the margin is 

 obscurely two-toothed, and the operculum apparently of two valves. In each of these cases it 



'Lehrburh <ler Xaturgesrhirhte, 1815, j>. !H. 



2 The nearly simultaneous apix-aranrf of tin- works of Lamouroux and l/amaivk have caused almost inextricable 

 confusion in the systematic- treatment nf this and t nther jrrrmps nf hydroids. See Part I, p. 54. 



3 A History nf I'.ritisli Animals, etc., Kdinl)ur>rli, 1S2S, ].. 545. 



*Cintnlnitiniis In the Natural History of the Tnited States, IV, ISIiL', ].. :!55. 



^Originally projiosid liv (Jray. IJsl of the specimens of British animals in the collections of the British 

 Museum, Part 1, Radiated Animals. London, 1847, p. 08. 



