198 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



itable by situations so clear that an old genus is untenable or a new 

 one practically unavoidable. 



Among the most recent discussions of the classification of the 

 Hydroida is that of Billard. 3 Billard somewhat severely criticizes 

 Stechow's work, introducing his discussion as follows : " Depuis les 

 travaux de Broch, un auteur allemand, Stechow, a complique les 

 choses en creant de nouveaux genres, en debaptisant et rebaptisant 

 certains genres, et ce d'une fagon qui n'a pas toujours ete heureuse et 

 judicieuse." 



He discards Stechow's genera Dymella, Sertaria, Pasya, Triden- 

 tata, Lagenitheca, Nigetta, and indicates the doubtful validity of 

 other genera established by that writer. 



With such differences of opinion between authors of recognized 

 authority it seems best to steer a conservative course. In this the 

 present writer finds himself more in agreement with Bedot and 

 Billard than with his distinguished colleague, Stechow. It seems 

 that this conservative course is less likely to add to the confusion 

 that prevails in our literature dealing with the classification of the 

 Hydroida than would follow the adoption of the great number of 

 nomenclatural changes instituted by Stechow. 



SYSTEMATIC REVIEW OF THE HYDROIDS 



[The asterisk (*) indicates a new species. The double asterisk 

 (**) indicates a new genus, while the dagger (f) indicates species 

 in which the gonosome is first described in this paper.] 



Gymnoblastic forms : 



TUBULAKIDAE. 



Branchiocerianthns imperator. Japan. 



EUDENDRIDAE. 



Eudendrium capWare. 

 Calypteroblastic forms : 

 Halecidae. 



Haleeium lighti. 

 Campanularidae. 



*Obelia thornelyi. 



Thyroscyphus marginatus. 

 Campanulinidae. 



Stcgopoma plicatile. 



Stegopoma gracilis. 



*Stegopoma dimorpha. 

 Hebellidae. 



Hebella contorta. 



Hebella veglecta. 



* Hebella spiralis. 



3 Note critique sur divers genres et especes d' Hydro Tdes, Kevuc Suisse de Zoologie, vol. 

 81, No. 2, May, 1924. 



