REPORT ON THE HYDROIDA. 
55 
Sertularia implexa grows in complex entangled tufts which attain a height of nearly 
three inches. The hydrothecae are borne close to the distal ends of the rather long 
intemodes, and their margin is divided into four triangular equidistant teeth, whose 
intervals support four very delicate, membranous, triangular valves, which, when in 
apposition, form a pyramidal roof over the orifice of the hydrotheca. The branches 
spring each from a point close to the base of a hydrotheca. 
Sertularia exigua , n. sp. (PL XXVI. figs. 2, 2a). 
Trophosome. — Stem monosiphonic, slender, much and irregularly branched, divided 
by well-marked joints into equal internodes, which are slightly inclined at an angle to one 
another, each internode carrying a single hydrotheca near its distal end. Hydrothecas 
alternate, distant, adnate to the internode for about half their height, then diverging at a 
rather wide angle, tumid below, much narrower and cylindrical towards the four-toothed 
orifice. 
Gonosome. — Gonangia borne by the interuodes near the bases of the hydrotheca, 
oviform, annulated, tapering below to a narrow point of attachment ; orifice tridentate, 
borne on a short tubular extension of the summit. 
Locality . — Station 75, near the Azores; lat. 38° 38' 0" N., long. 28° 28' 30" W.; 
depth, 450 fathoms. 
Sertularia exigua is a very slender profusely branched species. The internodes are 
inclined to one another at a slight angle, so that the stem presents a somewhat zigzag 
or geniculate form. The hydrothecae are distant, and present a sufficiently obvious 
character in their narrow cylindrical distal end with its four-toothed margin. 
The gonangia are in most cases distinctly annulated. Sometimes, however, the 
annulation is nearly obliterated. 
The species comes very near to Sertularia polyzonias, from which it differs chiefly in 
its much more slender habit and in the narrower and more elongated free portion of the 
hydrothecae. 
Sertularia polyzonias, Linnaeus (PL XXVI. figs. 3, 3a). 
Sertularia polyzonias, Linn., Syst. Nat. (Gruel.), p. 3856. 
„ ,, Lamk., Anim. sans Vert. (Ed. 2), t. ii. p. 142. 
Sertularella polyzonias, Hincks, Brit. Hydroid Zoopli., p. 235, pi. xlvi. fig. 1. 
Trophosome. — Stem monosiphonic, irregularly branched. Hydrothecae alternate, 
distant, adnate to the internode for about one-third of their height, then divergent, 
tumid below, contracted and cylindrical towards the quadrate, four-toothed orifice. 
