BY W. M. BALE. 767 



SYNTHECIUM ORTHOGOXIA, Busk. 

 (Sertularia orttioyonia, Busk, "Voyage of the Rattlesnake.") 



(Plate XVIL, figs. 1-5). 



Hyclrocatilus pinnate, attaining a height of about three inches ;. 

 iaternodes of the stem long, each bearing a pair of pinnae at the 

 summit, and one or two pairs of hydro thecse below (except the 

 lower internodes, which commonly bear a pair of pinnae only) ; 

 pinnae distant, opposite, widely diverge nt, divided into internodes, 

 each with one pair of hydrothecae. Hydrotheca* opposite, not in 

 contact but often approximate in front, tubular, adnate most of 

 their height, free part curved outwards more or less abruptly and 

 often produced horizontally ; aperture circular, vertical or directed 

 slightly upwards, margin entire, very slightly everted, usually 

 more or less marked with lines of growth. 



Gonothecse large, elongated, somewhat compressed in a plane 

 vertical to that of the hydrocaulus, with about 8-10 distinct trans- 

 verse undulations on the broader sides ; aperture terminal, very 

 small, without thickened border or distinct operculum. 



Hab.Off Ball's Head, Port Jackson. 



1 have no doubt that this is the Sertularia orthogonia of Busk, 

 though the free part of the hydrothecse is rarely produced outward 

 to so great an extent as in the type form. This abbreviation of 

 the hydrotheca tends to weaken the distinction between this 

 species and S. patula, nevertheless it is still open to doubt whether 

 they should be united. The hydrothecse of S'. orthogonia are 

 longer than those of 5. patula, and the adnate portion is decidedly 

 more erect, while the free part is curved outwards much more 

 abruptly, and the aperture is nearly or quite vertical, even when 

 the terminal portion of the hydrotheca is somewhat ascending. 

 The margin is not noticeably sinuated at the sides, and is marked 

 with lines of growth even in the terminal hydrothecae. In S. 

 patula the hydrothecse are smaller and are not abruptly flexed, 

 but are gradually curved outwards for most of their length, while 



