Some Northern Hydroid Zoophytes. 227 



is traversed by from three to five partial, and ill-developed septa, which 

 are arranged thus : one may be present at the base of the supracalycine 

 sarcotheca?, another, more strongly developed, occurs on the innermost 

 " corner " of the base, between these another may arise, while a fourth may 

 project downwards from about the middle of the base. A well-developed 

 septum, formed of two sections at right angles, separates the mesial sarcotheca 

 from the internodal cavity, and from the angle between the sections a 

 septum springs backwards into the internode. 



The hydrotheca? are close-set, almost symmetrical in lateral aspect, 

 wide at the base and opening out gradually towards the aperture, rather 

 deeper than wide. The profile is convex. The margin is carved in the 

 form described by Billard as sinusoide, being uniformly divided into 

 fourteen or fifteen exceedingly shallow denticulations by embayments as 

 shallow. There is no distinct intrathecal ridge, but the walls of the lower 

 two-thirds of the hydrotheca are more strongly built, and, downwards from 

 a definite line, assume a deeper stain in Eosin, so giving a characteristic 

 appearance to the hydrothecse. 



The supracalycine sarcotheca?, which taper downwards, reach just beyond 

 the margin of the hydrotheca. Their aperture is wide and scoop-shaped, 

 and their margin is minutely denticulate. The mesial sarcotheca is adnate 

 to the internode up to the base of the hydrotheca. It is free for about 

 a third of its length, has a scoop- shaped aperture, and a denticulate 

 margin. As has been mentioned, its cavity is separated from that of the 

 internode by a compound septum. Three fairly large cauline sarcotheca? 

 occur on each ioternode : two anterior — one at the base of the hydroclade 

 process, and one in the superior angle between it and the internode ; while 

 a third, which is posterior, opposes the latter of these two. The margins 

 of all are very minutely denticulate. 



No trace of gonosome occurred, and in its absence the species has been 

 referred, doubtfully, on account of its trophosome characters to the genus 

 Claclocarpus. 



Dimensions. 



Stem internode, length . . 065 — 0-71 mm. 



diameter . - 31 — 0'37 mm. 



Hydroclade internode, length . . - 62 — 65 mm. 



Hydrotheca, depth . . (Ml — 042 mm. 



diameter at mouth 



(lateral aspect) . 0'34— 036 mm. 



Locality. — From the neighbourhood of Iceland. 



VOL. XVI II. T 



