234! PEOF. p. M. DUNCAN S EEYISION OF THE 



The S. Hindostan Cretaceous species are nowplaced under Semi- 

 aster by Stoliczka. Feriaster, d'Orb., covers the same ground as 

 Linthia; but see A. Agass., 1883, Eeport on 'Blake' Echini, p. 77. 



EeGent,di?. Besoria, Gray, 1851 & 1854, Cat.Eec. Ech. Brit. Mus. 

 p. 58 ; and Feriaster, A. Agass. sp., 1883, 'Blake' Echini, p. 77: — 

 Australia, Tasmania, Pacific Islands (?) ; Arafura Sea, "W. Indies. 



Genus Schtzastee, Agassiz, 1847, Catal. Fais., Ann. d. Sci. Natr 

 vol. viii. ser. 3, p. 20. Desor, 1858, Synopsis, p. 389. A. 

 Agassiz, 1872-4, Revision, pp. 363, 609 ; 1881, Feport on 

 ' Challenger ' EcTi . p. 1 99 ; 1883, ' BlaTce ' Fch. p. 74. Loven, 

 1874, Etudes, pi. xxxi. 

 Syn. Opissaster, Pomel (pars) ; Feriaster, sensu A. Agass. 

 Test thin, small to large, tall to depressed, cordiform in tumid 

 marginal outline, sloping up to the posteriorly excentric apical 

 system ; highest behind and truncated or acuminate posteriorly, 

 may project there, slightly tumid actinally, with a broad and deep 

 anterior groove, which marks the dorsum. 



The apical system moderate in size, with two, three, or four 

 basal plates perforated, and the madreporite extending cen- 

 trally and posteriorly, and separating the posterior basal and 

 radial plates. 



Ambulacra diverse, the anterior in the groove and with close 

 oblique pores in pairs, either in a single row on either side or 

 confused and crowded : paired ambulacra petaloid, much sunken ; 

 the anterior flexuous, longest, only slightly divergent and extend- 

 ing forwards ; the posterior smaller and closer, often very small ; 

 the poriferous zones broad and closing distally. The ambula- 

 cral areas on either side of the long sternum are narrow. The 

 interradia are more or less gibbose and broad, and the second 

 and third plates of zone a of the right posterior area are fused 

 actinally. 



Peristome excentric in front, semilunar, witli a projecting 

 posterior labrum and a large amphisternum. Periproct in the 

 posterior truncation. 



Ornamentation close and homogeneous, largest actinally and 

 anteriorly. Spines short, slightly curved abactinally, and club- 

 shaped at the end, larger and longer actinally, a tuft over the 

 anal system, and two lateral tufts, rather close, at the end of 



