130 A NEW FAMILY OF HYDROIDEA. 



2. A New Species of Plumularia. 



This form was dredged l)y Mr. Wilson in Port Phillip, and differs, as far 

 as I can ascertain, from any yet described. In (1) that the nematophores are 

 perfectly independent of the hydrothecse, (2) that no intrathecal ridge is present, 

 (3) that the hydrothecae are cup-shaped, with smooth mitoothed margin, and are set 

 at some distance apart from one another, the form in question shows the features 

 characteristic of the group to which Alhnan gave the name of Eleutheroplea. 



The arrangement of the hydrothecfe would prevent it from being placed in any 

 of the three divisions — Isocola, Anisocola, and Monopyxis — into which Kirchenpauer 

 proposed to divide the genus. 



The species may be described as follows : — 



Plumularia procnmbens, n. sp. 



Hydrocaulus upwards of Pin. in length. The whole colony procumbent with 

 large polysiphonic branches running in a roughly horizontal direction. From 

 one side of these principally arise smaller polysiphonic branches, all lying in one plane. 

 From the sides of the branches arise numerous pinnae (at largest Jin. in length) 

 irregularly arranged ; in addition to these, hydrocladia (pinnules) may arise direct 

 from the hydrocaulus. Two pinnules, alternate, arise from each joint of the primary 

 pinnas. Pinnules composed of alternate small and large joints, the latter only 

 bearing hydrothecae and nematophores. Nematophores bithalamic with simple 

 terminal aperture, one beneath each hydrotheca, two at the level of the mouth of the 

 hydrotheca, all independent of the latter. Two nematophores in the angle between 

 the pinnule and main stem of the pinna; nematophores scattered irregularly in great 

 numbers over the surface of the polysiphonic stem and branches. 



Colour. — Light-brown stems. 



^& 



Hab.— Port Phillip, Mr. J. Bracebridge Wilson. 



The colony reaches a considerable size, and from the fact that the main branches 

 run in one direction (Fig. 20) with the smaller ones arising principally from one side, 

 it is inferred that in all probability it is procumbent in habit. The branches of the 

 hydrocaulus are all polysiphonic and strong, the pinnae and hydrocladia, which arise 

 from them, being very small indeed in comparison. The two latter are given off all 

 round the branches, and reach at most the length of \m., whilst the main branch 

 may be Gin. in length. 



Skeleton. 



(a) Structure of large branches (Figs. 24, 25, 26, 27, 28). 



