THE SKRTrLAKID.t:. 17 



The ornamentatit f tin- h\ -drothecal surface in tin- Sertularid;e i-- effected mainly by 



annulations, stria', ami reduplication-, of the maryins. am! each of the>e U conlinrd mainly to the 

 yenus X, rtiilin; Ilii. The rnyosit ie> are -oinet iines conlilied to the free part of the adcaiiline side, 

 as in X, ,-fiil,n;'ll,i ,/ni/,' (Plate XIV. tiy. 1). X. <<,/'<,/( I'late X\". liy. I ). ami A. catena (I'late XV, 

 liy. ."'). Often they are continued entirely around the hydro! heeal wall as in the ri/,/,,x,i yroiip. 

 Ordinarily this latter rondition i> associated \vith the quadrate neck, lint a notable exception 

 is found in a new species with very la rye barrel-shaped hydrotlieea'. .V. tiinii,n (I'late XVI. 

 tiy. 1). Annnlations dill'er from ruyo-,itie> in lieiny liner and more sharply cut, although tile 

 terms are often apparently used as if they were interchangeable. A notalile instance of thi> 

 style of ornamentation is found in l>!jili,ixi,i //vyi/.w (I'late XXX. liy. 1). in which the entire 

 hydrothecal wall is marked with very line but greatly raised annnlation.-. the outer surface of 

 which is so tine as to lie linear. If the liottoiiis of a pile of very thin dinner plates were 

 removed, and the remainder of the plates lilted to a cylinder, they would represent fairly well 

 the structure of these annular ridyes. There is hut one species that I know of with lonyitudinal 

 markinys like ribs or cost a', and that is X, rtnl,i,; ll,i ,n; i/i ( Plate XVII. tiy. ti). Stria' are simply 

 very tine aunulations rnnniny in a parallel direction. These are well shown in X, i-fnl,u; II <i 

 i/iiiii/i'n/ii ( I'late X\'. tiy. ."'). I'nder favorable conditions of illumination the entire surface of 

 the livdrolhccal walls is seen to lie marked by these tine, closely set line's. 



The hydrothecal aperture i^ laryely determined liy the shape of the niaryin and the maryinal 

 teeth. Most com moidy it is round or oyal in shape (liy. .".:'.); often it is i|iiadrate, as in the /</'/'" 

 y roil] i of X, rt nl a /: Ilii. or in X. quadfl'atdj rarely it is lunate, as in I'lni'mrm </!jf'ux,i (Plate X, Hy. '!}. 

 The niaryin is often more or less everted, as if rolled outward, as in the case of Synthecium 

 lnhitli, rum (Plate XLI. tiy. I): 01- i i may lie expanded, as in Sertularella pinnata (6.g. i'T) and 

 X. ,/,,/,i/ix (Plate XXIV. liy. 1); or sometimes it is contracted, as in X, rtiiliirin /,/*/(///*/' (Plate I, 

 tiy. 7) or .\l>;,l',ii,ir'i<i traski (Plate XXXIII. liy. Hi). 



The ornamentation of the hydrothecal niaryin is -ometimcs in the form of a distinct narrow 

 hand or rim. as in X rtuliin H<i fnnii<>x,i (tiy. L'L'). Synthecium rn-tuni (Plato XLI, fiy. '2), or X. / 

 f n/iii': Ilii ilixdnix (Plate XIX. tiy. ti); or it may lie effected liv means of closely approximated 

 circular striations, as in Abietinaria alexanderi (P\&te XXXV. tiy. ~>) oi 1 Synthecium marginatum 

 (Plate XLI. liy. 3). 



The reduplication of the niaryin often seen in the Sertularida'. lint displayed liest in ll<il-iiiin, 

 seems to lie j>rodueerl l>y pei'iodie and successiye .-tayes in the yrowth of the hydranth. or. as 

 Levinsen seems to have shown, by the successive renewal or regeneration of the hydranth. In 

 this latter case each reduplication represents a complete regeneration of the hydranth occupying 

 the hvdrotheea. These reduplications produce the appearance of a number of false maryins 

 In-low hut parallel with the functional one. There are many illustrations of this among American 

 forms. Midi as Synthecium /<//>//..<////. .V /////<//, II, i ,/it<i</i;it,i. ,s'. ,/, at if, /</ (Plate XX\ r . tiy. i'). 

 and >'. ,^/iij, Intnl. 



The maryinal teeth of the hydrotheca-. whateyer their oriyin or function, form a character 

 of the very yreatest importance from the standpoint of the systi-matist. and are therefore worthy 

 of careful consideration. They consist of more or less evident prominences projecting from the 

 niaryin and followiny in yeneral the direction of the hydrothecal walls from which they >priny. 

 They vary yreatly in si/.e. form, and position. Many hydrotheea 1 are entirely destitute of 

 maryinal teeth, in svhich case the niaryin is delined as even, plain, or sinuous. 



The even maryin is common in TTluiaria (tiy. :;'). S,l<t</!n<i]>xix. and . !/</'. tiit,ir!,i. and is present 



in all species of Si/i,lli,,-!niii thu.- far de.>crilied. It is oidy exeepli illy present in A, rf n/iifin. as 



X. il,xni,ii<l,x (Plate III, liy. 1). and in S, t -fnl,ii; ll,i. as in .V. f,inn<ix,i (liy. _'!') and X'. }i,irt/iinl>i. 

 The sinuous niaryin is found in several species of I >ij>/mxi,i, as in I>. i;ni,i,;,i.\\\ which the maryin 

 exhibits liroad and low undulations, which are not sufficiently pronounced to lie called teeth. 

 This form of maryin often produces the ell'ect of the mouth of a pitcher, and is usually found 

 in connection with the "pitcher-shaped" hydrotheca'. It is often very difficult to decide whether 



a yiven maryin is sinuous or toothed because the two completely interyradc. 



