A NEW FAMILY OF HYDROIDEA. 123 



Clathrozoon ivilsoni, n. gen. et. n. sp. 



Hydrophyton irregularly snb-dicbotomously branched, expanded in one plane fan- 

 shaped. Main stem somewhat flattened and ridged, arising from an expanded base, dark 

 brown in colour, with the surface showing a series of tortuous grooves. Smaller 

 branches cylindrical. The whole composed of a number of branching and 

 anastomosing tubes, with chitinous walls complete, except those of the most external 

 ones. Hydrothecfe, which have the form of tubular spaces with chitinous walls, 

 project slightly from the surface of all the branches, irregularly placed on 

 the main stems, spirally on the branches. The whole, except the external 

 openings of the hydrothecae, completely enclosed in a thin transparent chitinous 

 layer, from which arise very numerous cylindrical tubes enclosing the defensive 

 zooids, and which forms also a funnel-shaped collar, projecting beyond the lips of the 

 hydrothecae. 



Locality — Near Port Phillip Heads, Victoria. Mr. J. Bracebridge Wilson. 



The description of the species is the same as that of the genus, and I have much 

 pleasure in dedicating it to Mr. Wilson. 



The specimens were obtained from two spots, each within a distance of five 

 miles of Port Phillip Heads, tbat is, in Bass Straits, close to the Victorian shore. 

 They were dredged in water of from twenty to twenty-two fathoms, and were placed 

 directly into strong alcohol so that, like all received from Mr. Wilson, they are in 

 excellent histological preservation. The polypes are, of course, in a state of retraction, 

 and though very many sections from various parts of the hydrophyton have been cut, 

 nowhere as yet have I been able to detect the presence of reproductive organs, or of 

 individuals modified in connection with these, and though, therefore, unable to give 

 any account of the reproductive organs, I have thought it advisable to describe and 

 figure the animal carefully so far as can yet be done.* 



The largest colony secured by Mr. Wilson measures lOin. in height, by 4in. in 

 greatest width, and at first glance recalls to mind, to a certain extent, one of the 

 dark coloured fan-shaped gorgonid forms. A cursory examination, however, at 

 once shows that it does not belong to this group of animals. 



If the whole colony be secured, it is found to be attached by a broad flattened-out 

 base, attached to some solid structure; from this arises a single large stem, perhaps if in. 

 in thickness, slightly flattened out in one plane, and distinctly ridged (Fig. 1). From 

 the edge at either side of the plane lateral branches are given off, varying much in size; 



* That the animal is not at all common is shown by the fact that, though during this summer (1890-91), Mr. Wilson 

 has been kind enough to spend a considerable amount of time in dredging, with the special object of procuring more 

 specimens, not a trace of this hydroid has been brought up in the dredge, though the same ground which previously 

 yielded it has been visited. 



