HYDR01DA. - BALE. 17 



nntjiiH-nlata, All man, Journ. Linn. Soc., Zool., 

 xix., 1885, p. 144, pi. xvii., fig. 5-7. 



Dytiamena av^trnh'n, Kirchenpauer, Vevband. K. L.-C. Akad., 

 xxxi., 1864, p. 11, fig. 5 a-c. 



Sertitltin'it <insti-<tli, D'A. W, Thompson, Ann. Mag. Nat. 

 Hist. (5), iii., 1879, p, 105, pi. xvii., fig. 4, 4a ; Bale, Cat. 

 Austr. Hyd, Zooph., 1884, p. 72, pi. viii., figs. 7, 8. 



i>edintus, All man, "Challenger" Report., 

 Zool., xxiii., Hydroida, Ft. 2, 1888, p. 71, pi. xxxiv., 

 figs., 1 Ib. 



ia Challeityeri, Nutting, Amer. Hydroicls, The 

 Sertularida?, 1904, p. 54, pi. ii., fig. 1, 2; Billard, Ann. Sci. 

 Nat. (9), xi., 1910, p. 19, fig. 6. 



? Tk'in'aria heteromorpha, Allman, Journ, Linn. Soc,, Zool., 

 xix., 1885, p. 147, pi. xx., fig. 1-5. 



(Not Sertularia aHxtralis, Bale, Trans, and Proc. Roy. 

 Soc. Viet,, xxiii., 1887, p. 93.) 



Two forms of this most variable of the Sertularice, collected in 

 Bass Strait, represent perhaps the extreme limits of the species 

 in two opposite directions ; one, the ordinary small form, about 

 three-quarters of an inch in height, with the most widely 

 divergent hydrothecse found in any of the vai-ieties ; the other, 

 more attenuated in habit than any which I have previously met 

 with, reaching five or six inches in height, and with the 

 hydrothecfe narrow and but slightly divergent, 



I have referred previously to the small form (which is the 

 most abundant) as having the internodes of the pinnse bearing 

 only one pair of hydrotheca?, with the exception of one or two of 

 the proximal internodes on a few of the pinna?, which bear two 

 pairs. The stem-internodes are short, somewhat zig-zag, with 

 the nodes strongly marked, and the hydrothecse foi'ming the pair 

 are pretty close to each other ; indeed towards the upper part of 

 the stem they are often opposite and in contact, just as on the 

 pinnae. ThrouglKmt the polypidom the hydrothecse have the 

 upper portion strongly divergent ; often the bend outward is 

 quite abrupt, and beyond it the outer side rises in a sweeping 

 upward curve, which is continued to the point of the long outer 

 tooth. The aperture is elliptic and characteristically directed 

 forward and outward, not upward as in 8. macrocarpa and 

 similar species. The hydrothecse on the pinna? are strictly in 

 opposite pairs, and in contact in the front. 



