62 THE OCEANIC HYDROZOA.. 



SpHENOIDES AUSTRALIS. PI. IV, fig. 4. 

 Sphenia (mihi), 1851. 



Hydrophyllium wedge-shaped, presenting a sharp inferior edge and a wide superior 

 surface, produced into a point in the middle, round which four quadrate facets are 

 symmetrically arranged ; the two posterior are slightly e.xcavated and look backwards 

 and outwards. The two anterior look forwards and outwards, and are separated anteriorly 

 by a deep triangular notch. The posterior wall is broad and convex above, but ends below 

 in a point. It has four sides, the two upper of which are much shorter than the two lower. 

 The lateral faces are broad and irregularly pentagonal, their anterior edges being somewhat 

 concave. Close to the lower termination they give off a sharp downwardly directed point. 



The anterior face is occupied by the wide triangular aperture of the cavity of the organ, 

 which extends much further back in its lower than in its upper moiety, so that its posterior 

 contour is very convex forwards above, and equally concave below. 



Where this contour cuts the centre of the hydrophyllium the phyllocyst arises, and 

 is continued for more than half the distance to the apex of the organ, where it ends 

 in a point. Just above its origin it sends down in the middle line posteriorly a slender 

 caecum, which runs parallel with and close to, the posterior contour of the cavity, anfti ends 

 near its lower boundary. 



The gonocalyx has the form of a four-sided prism whose edges are produced into four 

 more or less marked crests, ending below in as many points, which surround a flat space in 

 which the circular aperture of the nectosac lies. The summit of the organ is roof-shaped ; 

 two of the faces of the prism being, as it were, bevelled off, and the calycine duct leads to one 

 gable end of this roof, by which, therefore, the gonocalyx is attached to the coenosarc. 



The elongated nectosac extends through the length of the prismatic portion of the organ, 

 and four longitudinal canals, ending in a circular canal around its mouth, run down its walls 

 from the calycine duct. It contains a large manubrium with well-developed ova or 

 spermatozoa. When the gonocalyx has attained its full size it becomes detached, and swims 

 about as an independent organism. 



Length of the hydrophyllium, half an inch. Length of the detached gonocalyx, one 

 fourth of an- inch. 



I first found this species on the 8th of February, 1848, in Bass's Straits, where 

 it abounded. Subsequently, I took it off Timor, and in different parts of the Pacific and 

 Indian Oceans. 



The individuals figured in PI. IV, fig. 4*, are probably only the young of the others. 

 I am strongly inclined to suspect that this is the Diphyozooid of J6i/la Basse?isis. In fact, the 

 hydrophyllium of the latter requires very little modification to convert it into that of 

 Sj)henoides. The abundance of the species in Bass's Straits is in accordance with this view.' 



^ I have briefly referred to the characters of this Diphyozooid, aud more particularly to those 

 of its reproductive organs, in my note, ' Ueber die Sexual organe der Dipbyden und Physopboriden,' 

 pubhsbed in Miiller's 'Arcbiv,' for 1851. 



