THE COLLECTION OE MISS H. GATTT. 149 



The features here noted ia Thuiaria polymorpha bring to mind 

 a phenomenon not unknown in the vegetable kingdom ; as in the 

 case of certain epiphytical orchids, in which flowers whose differ- 

 ence o£ form is such as to have caused them to be regarded as 

 characterizing so many distinct genera, are nevertheless found 

 associated in one and the same plant. 



TBECOCLA.DIUM, uov. gen. 



Generic character Trophosome. — Branching stems set with dis- 

 junct hydrothecse, and jointed at distant and uncertain intervals. Branches 

 having their origin within the hydrothecae. Gonosome, — Gonangia ovate 

 vesicles borne along the stems and branches *. 



The genus Thecocladmm comes near to Thuiaria, with which it 

 agrees in the indefinite length of its internodes. It difl'ers from 

 it in the very remarkable origin of the branches which invariably 

 spring from within the hydrothecse and extend through their 

 orifice. 



Thecocladium elabellum, n. sp. (PI. XIX. figs. 4>, 5.) 



Trophosome. — Colony composed of several simple or branched 

 monosiphonic stems, which arise at short intervals from a non- 

 adherent stolon. HydrothecsD alternate, adnate to the stem by 

 somewhat more than three fourths of their epicauline walls, cylin- 

 drical, curving gently forwards ; orifice entire, margined by a 

 membranous rim ; two or three pairs of hydrothecse borne by an 

 internode. 



Gonosome not present. 



Locality ? 



The short, somewhat robust stems, which on the specimen 

 attain a height of about 1 inch, carry deep cylindrical hydrothecae, 

 slightly turgid at the base. These curve gently forwards, and 

 present a perfectly even circular orifice. The orifice is sur- 

 rounded by a broad ring-like membranous rim. 



A remarkable feature of the present species is the existence of 

 a delicate chitinous annular diaphragm, which intersects the 

 hydrotheca obliquely, passing from about the middle point of 

 the anterior wall downwards and backwards to a point on the 

 posterior wall a little above the base of the hydrotheca. I am 



* No gonosome was present in the specimen contained in Miss Gatty's collec- 

 tion ; and the character here given is derived from an example of this genus 

 collected during the voyage of the ' Challenger.' 



LINN. JOUEN. — ZOOLOGY, YOL. XIX. 12 



