12 SYDNEY J. HICKSON AND F. H. GRAVELY. 



The fortunate preservation of a small and probably young branching stem of 

 specimen A, with gastrozooids at its proximal end similar to those of the basal parts 

 and at its distal end similar to those of specimen B ; with a smooth surface similar to 

 that of specimen B, and ramifying and growing without any axial support as 

 specimen B does, may be regarded as conclusive evidence that the specimens belong to 

 the same species. 



The species resembles Hydmctinia in having sessile hydranths, a thick membranous 

 hydrorhiza covered with a continuous sheath of ectoderm and provided with a lacunar 

 chitinous skeleton, and in having adelocodonic gonophores. 



On the other hand, it differs from many of the species of Hydractinia in 

 forming large unsupported rhizocauline branching stems, and in the absence of 

 dactylozooids. 



A species that has close affinities with H. dendritica is //. angusta, from 71 S. and 

 87 W. 400 metres (Hartlaub 9: pp. 7-8 ; PL IV., figs. 1-6). It forms branching (?) 

 cylindrical rhizocauline stems. It has also tentaculate blastostyles and no dactylo- 

 zooids. But it has thorny processes on the surface, which in our species are confined 

 to the basal part ; the gastrozooids of our species are quite twice as large and the 

 tentacles are more numerous than in Hydractinia angusta. 



It differs from Hydrodendrium gorgonoides (Nutting 20: pp. 936-938; PL I., 

 figs. 1-6 ; PL VII., figs. 1-2) from Hawaii, in having definite blastostyles, in the 

 presence of a large hypostome on the gastrozooid, in the colonies being unisexual, 

 and in other characters. It resembles Hydrodendrium in the occurrence of branching 

 brittle rhizocauline stems, in the absence of spines on the surface, and in the 

 absence of dactylozooids. 



Hydractinia angusta and Hydractinia dendritica form two interesting links in a 

 chain connecting the ordinary species of Hydractinia with Hydrodendrium. It may be 

 noted here that in addition to the species of Hydractinia mentioned above that have no 

 dactylozooids, Hydractinia parvixpina (Hartlaub), //. carnea, var. inermis, H. humilifi, 

 and //. provuti (Koss.) are said to have no dactylozooids ; and in other species described 

 by Bonnevie (6), Hincks (11), and Allman (2) no mention is made of these peculiar 

 zooids. The presence of dactylozooids cannot therefore be regarded as a character of 

 the genus. 



FAMILY TUBULARIIDAE. 



GENUS TUBULARIA (Linn, emend. Allman). 



We have found in the collection what appear to be three distinct species 

 of Tubularia, but of these, one is represented by a single hydranth, and one 

 by two hydranths. The third species agrees fairly well with the description given 

 in Bale's Australian Zoophytes of a species described in MS. by Halley from 

 Hobson's Bay. 



