" ENDEAVOUR " SCIENTIFIC RESULTS. 188 



Mesial savcotheca very small, adnate to the base of the 

 hydrotheca, free projecting portion very short, with terminal 

 and inferior apertures which are generally distinct though 

 closely approximate. Lateral sarcothecaB very small, ovate, 

 closely adnate, apertures as in the mesial. Cauline sarcothecse 

 similar to the laterals, but larger, two at the base of each 

 hydrocladinm in front and one behind the axil. 



Gonothecas borne at the bases of the hydrocladia small, ovate, 

 slightly flattened on the summit. 



Colour.— Whitish. 



This species is very closely allied to H. vegce, notwithstanding 

 the marked dissimilarity in the hydrothecaa of the two species. 

 The peculiar system of ramification agrees closely with that of 

 H. vegce, and the description need not be repeated. But whether 

 the species ever attains a size approaching that of H. vegce, or 

 develops a distinct fascicled stem, is not apparent. I saw only 

 a few fragments, not exceeding an inch and a half in height, and 

 branching about twice, and the supplementary tubes which 

 originate from the branching points had in scarcely any cases 

 reached the next branch below. 



The long slender hydrothecaa are of graceful form and delicate 

 texture, the free distal portion being so collapsible that few of 

 them have, in the mounted specimens, retained their original 

 form. The denticulation of the border varies greatly, being 

 sometimes almost wanting. In lateral view there appears at first 

 sight to be a distinct intrathecal ridge; closer scrutiny however 

 shows that this is a narrow process, triangular in front view, 

 which projects freely into the cavity of the hydrotheca from the 

 margin of the hydropoi*e, and corresponds with the small 

 perisarcal flaps found in a similar position in H. vegu'. 



The specimens were found mixed with a cluster of shoots of 

 Aglaophenia tenuissima, but were detached ; it is uncertain, 

 therefore, whether the association was accidental or whether the 

 colony had established itself on the Aglaopheiiia in the fashion 

 of so many other species of the genus. 



A very closely allied species is II. expansa, Jaderholm 

 (Aussereuropaische Hydroiden im Schwedischen Reichsmuseum). 

 which however seems to be a far larger and more robust form, 

 while the hydrotheca; have the adnate portion not nearly so 

 elongated and the distal portion much less strongly curved away 

 from the hydrocladinm than in the present species. It is found 

 in the Japanese region. 



Loc. — Great Australian Bight, Long. 130^40' E, 16U fathoms. 



