196 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



and Zygophylax curvitheca was from 400 fathoms, station 5664. 

 Macassar Strait, 4° 31' 22" S., 118° 53' 18" E. Nearly all of the 

 other hydroids secured during this cruise were from depths of less 

 than 200 fathoms and most of them from under 50 fathoms. 



Hydroids were taken at 58 of the 575 dredging stations reported 

 for the cruise, which does not indicate an extraordinarily rich 

 hydroid fauna. 



The author takes pleasure in expressing his great obligation to 

 Warren Keck, research assistant in zoology in the University of 

 Iowa, for very efficient aid in the preparation of this paper, whereby 

 the writer has been relieved of most of the drudgery of looking 

 up references, preparing specimens for examination, verifying data 

 regarding dredging stations, and looking up the literature regard- 

 ing previous work on the Hydroida. Much of the accuracy of 

 the paper is due to the care and fidelity with which Mr. Keck has 

 discharged his duties as research assistant. The plates accom- 

 panying this paper are from drawings by Mr. Keck. 



In the matter of classification the writer adheres in the main, so 

 far as the families Campanularidae, Sertularidae, and Plumularidae 

 are concerned, to the scheme adopted in his American Hydroids, 

 Parts I, II, and III, although he has used some of the genera insti- 

 tuted by Stechow and has added one new genus, Stechawia. 

 Stechow 1 has worked out an elaborate revision of the classification 

 of the Hydroida in which he has divided the family Sertularidae 

 into three new subfamilies, Thyroscyphinae, Sertomminae, and Sertu- 

 larinae, largely on the basis of the presence or absence of an abcauline 

 blind-sack in combination with certain characters of the hydrothecal 

 margin. He recognizes 36 genera in this family of which 14 are 

 new. He also reduces to synonymy a large number of generic names 

 that have been established and almost universally used for genera- 

 tions, such as Thuiaria, Desmoscyphus, and Monopoma. 



While I do not propose to enter into an adequate discussion of 

 Doctor Stechow's work, I will say that it seems to me that some of 

 his genera are based on characters that are not of generic rank, and 

 in his new genus Tridentata, 1920, he has included a large number 

 of heterogeneous forms that, in my opinion, are generically separate. 

 In this single genus he has placed together species formerly belong- 

 ing to the well-established genera, Sertularia, Dynamena, Desmoscy- 

 pkus, Thuiaria, all of which seem to me to have generic rank. He 

 places this heterogeneous lot under one genus because they have two 

 lateral hydrothecal teeth and a small adcauline median tooth, 

 together with a two-flapped operculum. The old genus, Sertularia, 

 is practically identical with his Tridentata except in the possession 



1 Zur Kenntnis der Hydroidenfauna des Mittelmeeres, etc., Parts I and II, 1919-1923. 



