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



This species is rather larger, broader, and flatter than A. calcai\ 

 with only six, less deflned rays, scarcely projecting beyond the only 

 slightly indented or moderately concave intervening sides, and is 

 fiu'ther easily distinguished by the two spines, instead of one, on 

 all the midtUe interambulacral ossicles below. It inhabits the same 

 parts of the shore as A. calcar, but is not quite so common. 



Explanation of Fiodres. 



Plate 200. — Fig. 2, ordinary specimen, riewed from above, natural size, showing spinulose 

 crescentiform plates. Fig. 2a., portion of underside, natural size, showing the pair of diverging 

 spines on all tlie middle interambulacral plates, and the marginal row next the adambulacral 

 plates with single larger spine, and pairs of more slender adambulacral spines, and the groups of 

 longer spines on the oral plates. Fig. 2b, madreporiform tubercle, magnified three diameters. 

 Fig. 2c, median interambulacral plates, each with its pair of diverging spines, magnified three 

 diameters. Fig. 2d, pairs of spines on adambulacral plates, magnified three diameters. Fig. 2e, 

 group of ten spines on edge of one of the six interambulacral oral plates. 



Plate 200, Fig. 3. 



PENTAGONASTER (TOSIA) AURATA (Gray). 



The Twelve-plated Shield-Star. 



[Genus TOSIA (Gray). (Sub-kingdom Radiata. Class Echinodermata. Order Asteroidea 

 Family Pentagonasteridae. Sub-family Pentagonasterinae.) 



Gen. Char. — Body flat, pentagonal, sides approximately rectiliaear, sUghtly concave between 

 the blunt tips of the rays. Two rows of marginal plates, few, smooth, with one row of granules 

 on edge ; abactinal or dorsal area and interambulacral plates below covered with rounded or 

 polygonal smooth or granulated plates. Ambulacra margined by three or four rows of short 

 spinules. Anal aperture very minute on right posterior edge of dorsocentral plate when madre- 

 poi'ite is placed in upper right-hand interradium.] 



Description. — Sides gently concave. Dorsal plates flat, irregularly polyg-onal, 

 rounded, close, each with one row of blunt granules round the edge ; three or five 

 rows running- to the angles slightly larger and more regularly hexagonal than the 

 intervening ones ; all diminishing towards the margins; closely touching, especially 

 below ; four basilar ones near the middle larger than the rest, one opposite the 

 middle of each side, but the fifth, near the madreporite, not conspicuous. Madre- 

 poriform tubercle subtrigonal, the angles truncated, entirely covered with minute 



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