Zoology.'] NATURAL HISTORY OF VICTORIA. \_Polyzoa. 



Plate 68, Fig. 1. 



IDMONEA MILNEANA (D'Orbigny). 



[Genus IDMONEA (Lamx.). (Sub-kingd. Mollusca. Class Polyzoa. Order Infundibulata. 

 Sub-order Cyclostomata. Fam. Idmoneidae.) 



Gen. Char. — Polyzoary erect, branched. Cells tubular, arranged in parallel transverse or 

 oblique rows on each side of the mesial line of the front of the branches.] 



Description". — Polyzoary spreading- more or less horizontally, branches broad, 

 flat, dividing- dichotomously ; cells usually four in a series, the outer the long-est, 

 surface closely punctate ; back of branches longitudinally grooved, finely punctate 

 or perforated, and marked with transverse concentric ridges of growth. 



Reference. — Busk, Brit. Mus. Cat., pt. iii., p. 12, Plate xi. 



Port Phillip Heads, 10-15 fatlioms. 



The largest specimen I have seen is the one figured. The 

 polyzoary is green, 1 inch in one diameter by f in the other. 

 It springs from the surface of a Retepora and immediately 

 branches horizontally and dichotomously. These branches send 

 down from the back numerous calcareous radiciform processes 

 which become attached to the Retepore. The branches are 

 broad and flat behind. The cells are usually four in a series, the 

 inner the least prominent, the others gradually increasing in 

 length to the outer which projects very much. They are united 

 side to side throughout almost their whole length, so as to form 

 regular walls rising up and projecting far beyond the edges of the 

 branches. They are distinct on the front of the branches and are 

 minutely and closely punctate. The back of the branches is 

 longitudinally sulcate, thickly covered with punctations which are 

 usually opened and form small pores, and it is closely marked by 

 nearly transverse, arched, concentric lines of growth. From 

 various parts of the back of the branches calcareous radiciform 

 processes project downwards, and are united to the body from 

 which it grows ; these processes are sulcate and punctate, and in 

 section are seen to be composed of a number of prismatic tubes. 



Explanation of Figures. 



Plate 68. — Fig. 1, specimen, natural size. Fig. la, portion of front of same, magnified. 

 Fig. 16, portion of back, magnified, showing the longitudinal sulci, punctations, and transverse 

 ridges. 



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