SHALLOW-WATER STARFISHES 285 



Actinal plates are usually rather numerous and tesselated or 

 imbricated. Adambulacral spines are usually numerous and papilli- 

 form or spiniform. A distinct dorsal pore (pseudanus) is usually 

 present. Genital pores generally ten, usually all separate, situated 

 in the dorsal interradial areas ; sometimes serial on the sides of the 

 rays. Oral plates usually large and convex on the actinal surface. 



Superambulacral plates are present in some genera, absent in 

 others. The existence of superambulacral plates has formerly been 

 supposed to be characteristic of the Astropectinidae only, but they 

 exist in several of the genera here referred to Valvulosa (viz., 

 Mediaster, Dy taster, Pseudarchaster, etc.), and in other groups. 



Adambulacral plates wide, with a longitudinal group of small 

 furrow-spines and with one or several spines on the actinal side, 

 often becoming much longer distally. Dentary or jaw-plates large 

 and usually convex on the actinal surface, bearing numerous oral and 

 epioral spines. 



Ambulacral feet large, with suckers. Owing to the generally close 

 union of the ossicles, especially of the large marginal plates, most 

 of these starfishes are rather rigid, showing much less flexibility than 

 in most other groups. The Ophidiasteridas are exceptional in this 

 respect, for they are mostly very flexible. 



Family GONIASTERID/E (Forbes), emended Verrill. 



Goniasteridce (pars) Forbes, 1840. Verrill, Trans. Conn. Acad. Sci., i, p. 343, 



1867. Perrier (pars), Revision, Arch. Zool. Exper. et Gen., iv, pp. 281, 



283, 289, 291, 1875 ; op. cit., V, p. I, 1876. 

 Pentagonasterince Viguier (pars), subfamily, op. cit., vii, p. 166, pi. x, figs. 



20-25, 1878. 

 Pentacerotidce (pars) Gray, Synopsis, p. 5, 1866. 

 Pentagonasterid<E (pars) Perrier, op. cit., p. 231, 1884. Sladen (pars), op. 



cit., pp. 260, 264, 1889. 

 Goniasteridce Verrill (restricted). Revision, in Trans. Conn. Acad. Sci., x, 



p. 14s, 1899 (non Viguier). Fisher, op. cit., 1911&, p. 158. 



Phanerozonate starfishes usually having a rather broad, flat or 

 slightly convex, rather rigid disk, sometimes nearly pentagonal in 

 form, but often stellate with more or less prolonged rays. Mar- 

 ginal plates usually large and thick, forming a thick, nearly vertical 

 margin, the two rows equal or subequal. 



Dorsal plates various, but usually tesselated, polygonal, or round- 

 ish, sometimes lobed or substellate, or united by internal ossicles. 

 They are commonly granulated or protopaxilliform, sometimes 

 spinulose, or bear tubercles or spines ; rarely naked, or covered with 

 soft skin, with or without granules or pedicellariae. 



