THE SERTt'LARID.<. 



49 



Bathymetric distribution. Here a '/a in ii has seemed best not to follow tin- scheme adopted 

 in discussing the Plumularidee, on account of the yivui preponderance of -Imllou \\aier forms in 

 the Sertularida-. and also for (lie reason that the talile Driven for the I'lumularida- iuvolve<l more 

 labor than is necessary in the case of other species. I>y Divine- the maximum and iniiiiiiiuni 

 depth at wliicli eacli species is found il i- thought thai I lie la Me will lie as u-eful as that Driven for 

 the Plumularidae, in which the record is maintained for all the interiliediate /.ones, it bein^. indeed, 

 more probable that tin- actual condition-* of batlivmctrie distribution are thus presented, a-, it is 

 altogether more likely that the nonoccurrence of a species in the table given I'm -the Plumularidse 



is due to incomplete exploration than that the ha thy met ric distribution of these specie-, U actually 

 discontinuous, as would be indicated b\ that table. In other words, we have a riylit to consider 

 that a species that has been reported from IHII and ::iu fathoms actually exists somewhere at a 

 depth of :.'nii fathoms, or that it has recent l\ existed at that depth. 



In comparing the two tables it becomes at once apparent that the Sertul:irid;c are much 

 more generally found in shallow water than the Plumularida-. The proportion of .-hallow- 

 water forms that is. those found in less than .".u fathoms lioinu- a little over !:< per cent in 

 the Sertularida- and .">u per cent in the Plumularidee. Tliere are 41 per cent of the Sertularida- 

 contined to the shallow-water /one. while there are only M:! per cent of the I'luniularida' confined 

 to the same /one. 



The following table shows very plainly the difference in the bathymetric distribution between 

 the two families: 



ti <; distribution <>/ ///'/, </.<///</ 



The following species of Sertularidie ha\e been di-edo-ed at depths greater than .".ui i fathoms: 

 in fnll,i.i\ l.iilo fathoms (lionnevie); /)iji/ntniti tiinnirixl-n, titio fathoms (Honncvie): 

 s, rfiiliii'i-llii i-liinmi. (iiii) fathoms (Allman); SertulareHa tricuxj)/'ifiifii, t.:;7"i fathoms (lionnevie); 

 S, rfnliii'' l/ii ti-njiii-ii. l.ltis fathoms (Clarke). 



Th(> well-known S,rfi/I<ir</l<i t i-i<-iix/iiil<il<i seem> to have the u-reatcst \-ertical distribution of 

 any sei'tularian. ran;-in^ from the littoral region to the depth of l,3T;i fathoms. The only 

 American hydroid that has been found at :i "Teater depth than this is Aglaophenopsis verrilM 

 Nuttinjj. which was found at l,74i^ fathoms. In this case, however, the known bathymetric 

 range is from 1,-iHT to 1,7-k.' fathoms.' 



SERTULARIA Linnaeus (modified). 



Traji/H iftiini- . II ydrolheca- in strictly opposite or rarely siibopposite pairs. Stem and 

 branches normally divided into regular internodcs. each of which bears a pair of hydrothecffi, 

 but sometimes there are more than one pair lo the internode. in which case the h\ drotln-c;e are 

 strictly opposite. Open-ilium normally of two Haps. 



(fnniixiiiiii . Gonangia oval or ovate, with a short collar and broad aperture and no internal 

 marsiipium. An acrocyst is occasionally present. 



This beiny the original Limia-an u'enus for the hydroids. it has necessarily siill'ered many 

 vicissitudes, most of which lia\'e been iii the direct ion of closer and closer delimitation. Lamouroux 

 leading by separating what are now known a- the 1'lumulariihe and also breaking the Sertularians 

 propel' into two e-roiqis. [h/mum im to include those \vith strictly opposite bydrothecsB, and 

 S'< rfiiliir/ii those with more or less alternate hydro! hec;e. ' \Vere both these generalised in tin- 

 present work, the species that I include in X rl l<n-i<i would jjo into the yemis Dynamena. 

 Lamouroux aNo set aside the ~pecie- no\\ included in the I lalecida- in thee-enus '/'/"/. aflerward- 



- r.iillctin philomatique, 181L'. 



