11 



XVII. Pentagonasteb. Body formed of convex, smooth, 

 and spineless ossicula ; the ossicula of the underside with 

 a central sunk line with a central perforation and a small 

 pit at each end. The marginal ossicula near the tips of 

 the rays very large and swollen. Gray, Ann. N. H. 1840, 

 p. 280. 



1. Pentagonaster pulchellus (T. 8. f. 3). Body with five 

 deeply concave sides, with fom- oval convex tubercles on each 

 side, and a small one interposed between the anglcsof each of 

 them. Gray, Ann. N. H. 1840, p. 280. Astrogonium pul- 

 chellum, Midi. ^ Trosch. 55. Asterias Miilleri, Agassiz, 

 MS. (Mus. Paris). Stephanaster elegans, Ayres, Proc. 

 Boston Soc. N. H. Astei'ias pulchella. Gray, Encycl. Me- 

 trop. t. . f . . Inhab. China. 



When the large apical tubercles have been injured, they 

 become divided into small unequal ones. 



2. Pentagonaster abnormalis (T. 8. f. 1, 2). Body penta- 

 gonal; sides deeply concave, with eight narrow oblong 

 ossicula on each side ; the apical ossicula about twice the 

 size of the others. Inhab. . 



3. Pentagonaster Dubeni (T. 3. f. 2). Body flat, 5-rayed; 

 rays two-thirds the length of the diameter of the disk, 

 rounded at the end; ossicula all convex, rounded. Mar- 

 ginal ossicula }j], large, round, those near the end of the 

 arras largest and most convex. Gray, P. Z. S. 1847, p. 91 . 

 Inhab. Western Australia. 



This species differs from P. pulchellus in the marginal 

 ossicula being more equal, and in the arms being much 

 longer and more slender. The ossicula of the dorsal disk 

 are unequal in size and rather ii'regularly formed ; those 

 near the margin on the middle of the sides are oblong and 

 narrow ; those of the oral sm-face are more regular and not 

 so convex, those near the angles of the mouth being the 

 largest and subtriangular. I have named this beautiful 

 species in memory (I regret to say) of M. W. von Diibeii, 

 who recently published a very admirable paper on the 

 northern species of this family. 



See a. Astrogonium crassissimum, M'dbius, Abhandl. iv. 

 18G0, p. 81, t. 2. f. 1, 2, is the same or an allied species, b. 

 Astrogonium magnificum. Mull. &; Trosch. Ast. 53, t. 4. 

 f. 1. c. Astrogonium astrologorum, Miill. ^' Trosch. Ast. 54;. 

 d. Astrogonium geometricum, Milll. ^y Trosch. Ast. 54. 



XVIII. TosiA. The body formed of smooth and spine- 

 less ossicula, rather convex ; the dorsal and ventral ossicula 

 entii'e, without any impressed line, subequal ; the marginal 

 ossicula two-rowed, with a small intermediate one near each 

 tip; dorsal wart triangular. Gray, Ann. N. H. 1840, 

 p. 281. 



The granules between the ossicula are deficient in the 

 dead and washed specimens. It has been thought that the 

 fossil species found in the chalk belonged to this genus ; 

 but the sm'face of the ossicula of most of the specimens I 

 have seen show, from the scars with which their surface is 

 covered, that they were covered with gi-annles ; therefore 

 they rather belong to the restricted genus Astrogonium. 

 Gray, P. Z. S. 1847, p. 80. 



* The ossicida of the oral disk are more or less entirely 

 covered loith crowded, flat-topped granules. 



1. Tosia grandis (T. 3. f. 1). Dorsal ossicula very un- 

 equal, flat-topped. Marginal ossicula j| or jg on each 

 side, rather convex ; the ossicual of the oral surface are 

 furnished with two or three rows of crowded granules, and 

 those near the ambulacra are most covered. Gray, P. Z. S. 

 1847, p. 80. Inhab. Western Australia. 



Linck, under the name of P. rcyularis, t. 13. f. 22, 23, 

 copied (E. M.t. 96, and Seba, iii. t.'8. f. 4) a species some- 

 what like the above, but it has only ten marginal plates. 

 Miiller, who thought he examined Linck's specimen at 

 Leipsic, describes it as having seven upper and five under 

 marginal plates. Goniodiscus stella, Mobius, Abhandl. iv. 

 1860, p. 9, t. 3. f. 1, 2, is a very nearly allied species. 



2. Tosia aurata (T. 16. f. 2). Golden yellow. Dorsal 

 ossicula flat-topped, the five in the centre, between the cen- 

 tral lines of the arms, largest and round; the marginal ossi- 

 cula fji or f|, rather convex and nearly equal (that nearest 

 the top not being longer than the others) ; the ossicula of the 

 oral disk, all except a few in the middle of each area, 

 entirely covered with flat-topped granules. Gray, P. Z. S. 

 1847, p. 80. Inhab. Australia (Brit. Mus. three spec). 



** The ossicula of the oral surface are only edged ivith a 

 single series of granules, like those of the back. 



3. Tosia tubercularis {T.16.f. 4). Yellow, edges i-eddish. 

 The dorsal ossicula convex, subtubercular, those of the 

 centre of the arms highest, those between the arms in the 

 centre largest, nearly flat. The marginal ossicula Ji or g 

 on each side, convex, subtubercular ; the one near the top 

 of the arm largest and oblong, longitudinal, convex. The 

 ossicula of the oral surface small, each suiTounded with 

 a single series of granules. Gray, P. Z. S. 1847, p. 91. 



Var. ? or young ? The ossicula of the oral surface near 

 the edges covered with granules. Inhab. Swan River. 



There is a specimen in the British IMuseum with six 

 marginal ossicula very like the above, but ditt'eriug from 

 it in the dorsal ossicules only being convex and rounded ; 

 it has the same convex and large marginal plate. Gray, 

 P. Z. S. 1847, p. 80. 



4. Tosia rubra (T. 16. f. 3). Red brown. Dorsal ossicula 

 rather Convex, rovmded. Marginal ossiciila J-{J on each si^ 

 rather convex, equal, that at the tip of each arm smaller, 

 narrow ; the ossicula of the oral surface flat-topped, with 

 a single series of marginal granules. Gray, P. Z. S. 1847, 

 p. 81. Inhab. Australia. 



5. Tosia australis (T. 16. f. 1). Yellowish or reddish. 

 Dorsal ossicula rather convex, rounded. Marginal ossi- 

 cula [i ou each side, rather convex, equal ; the ossicula of 

 the oral surface flat-topped, with a single series of marginal 

 grannies. Gray, Ann. N. H. 1840, p. 281 ; P. Z. S. 1847, 

 p. 81. Astrogonium australe, Miill. ^ T)'osch. Ast. 55. 

 Inhab. Western Australia, Swan River. 



See a. Astrogonium ornatuui, 31iill. i^- Trosch. Ast. 55. 

 6. Asti'ogonium Lamarckii, Miill. S^- Trosch. Ast. 56. 



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