Zoology.'] NATURAL HISTORY OF VICTORIA. [Echinodermata. 



vermicular and branched ridges, situated at about one third the distance from the 

 centre to the margin. Marginal plates flattened, only slightly convex, with one row 

 of granules round each; plates rather larger at middle of sides than at salient angles 

 or tip of rays, twelve to fourteen above, and twelve to sixteen below from tip to tip 

 of rays; one small odd plate in middle above. Oral actinal or under-plates closely 

 touching, generally covered completely with granules, but some few with smooth 

 central portion, with one, tvvo, or three rows of granules on margin; two rows of 

 blunt spines and two rows of granules larger than the rest bordering the ambulacra 

 on each side (two compressed blunt spines on inner face of each adambulacral plate, 

 and two shorter behind them). The five triangular mouth plates are bordered with 

 spines like those of the adambulacral plates, within which are thick prismatic 

 granules. From mouth to tip of ray (R), taken as 100, from same point to middle of 

 side (r), y^% to -Ytru; average diameter, '2 in. lines. Colour: Often rich yellowish 

 orange ("old gold"), more commonly clouded more or less with dull purple. 



Reference.— P.Z.S., 1847, p. SO; Gray, Synop. sp. St., t. l(i, f. 3. 



The genus Tosia of Gray, taken as a sub-genus of Penta- 

 gonaster by Perrier, and merged into that genus by Sladen, is a 

 convenient group or subdivision of the larger genus, which I think 

 may advantageously be continued. 



The Shield- Stars, as the flattened pentagonal Starfishes with 

 large marginal plates and no projecting rays are called, are common 

 on our shores, two species of the present genus being abundant 

 under stones a little below low-water mark in Hobson's Bay, and 

 along the rocky outer shores, the present species being distin- 

 guished from T. Australis, by its more numerous and flatter 

 marginal plates (only six in T. Australis) and the greater number 

 of plates below being covered with granules ; some specimens 

 having all on the actinal side granulate, and others having few or 

 many smooth in the middle, with one, two, or three rows of 

 granules round the margin. There are usually twelve marginal 

 plates above and below on each side between the points of the 

 ambulacra, and where they are more numerous the additional 

 plates near the apices, are much smaller than the others ; the plates 

 towards the middle of the sides are always perceptibly larger than 

 those near the angles. 



I note that M. Perrier in the "Annales des Sciences Naturelles" 

 for 1885, finds the marginal plates varying from eight to fourteen 

 in his Pentagonaster Gosselini and this agrees with my experience 

 of this present species, showing that the character varies more 



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