FROM THE LOWER WHITE CHALK. 179 



in PL XXVIII, fig. 2 a. The spines are slender, cylindrical, finely striated, and granulated ; 

 the longest exceed If inches in length, and are less than the twelfth of an inch in diameter . 

 some of the spines are bent, as in figures 3 and 4, some are spatulate (fig. 2 b), and others 

 are forked (fig. 2 c) at their extremities. The base of the spine around the milled ring 

 has fine longitudinal lines extending a short distance up the stem, which is likewise covered 

 by finer microscopic lines (fig. 2 d, and figs. 3 and 4) extending along the stem. 



Affinities and Differences. — This species very much resembles S. gibba ; but, according 

 to Dr. Woodward, it is entirely distinct from the mould of Professor Agassiz's original 

 example of that species. 



Locality and Stratigraphical Position. — Salenia Clarkii is very rare in the Grey Chalk 

 near Folkestone ; from this " terrain " the specimens in the Royal School of Mines and the 

 British Museum were obtained. 



History. — First named by the late Professor Edward Forbes, in his additions to the 

 Echinodermata in the 2nd edition of Professor Morris's Catalogue of British Fossils. 

 A diagnosis of the species was subsequently drawn up by Dr. Woodward, in his Appendix 

 to Decade V, Memoirs of the Geological Survey, illustrative of Organic Remains. It is 

 now figured in detail from specimens contained in the Cabinet of the Rev. T. Wiltshire, 

 F.G.S., and in both our National Collections. 



b. — Species from the Lower White Chalk. 

 Salenia granulosa, Forbes. PI. XLI, figs. 2, 3 ; PI. XLIII, fig. 1 a — h. 



Salenia scutigera, Forbes. In Dixon's Geol. Foss. Sussex, pi. 3-40, pi. xxv, fig. 24, 

 1850. 



— heliophora, Sorignet. Oursins de l'Eure, p. 20, 1850. 



— granulosa, Forbes. In Morris's Catalogue of Brit. Foss., p. 89, 1854. 



— — Woodward. Mem. of Geol. Surv., Dec. V, 1856. 



— incrustata, Cotteau, in Desor's Synops. des FJch. foss., p. 152, 1856. 



— granulosa, Pictet. Traite de Paleontologie, t. iv, p. 218, 1857. 



— — Cotteau. Paleontologie Francaise, Terrain Cretace, torn, vii, 



p. 167, pi. 1039, figs. 6—21, 1860. 



Diagnosis. — Test small, circular, depressed, upper surface convex, under surface flat; 

 ambulacra narrow, slightly flexed, with two rows of marginal mammillated granules ; inter- 

 ambulacra wide, much covered by a prolongation of the ovarial plates, tubercles small, 

 surrounded by areolas ; apical disc very large, covering like an incrustation nearly the 

 entire upper surface; the flat ovarial plates have flexuous lines of granular processes 

 diverging from their centres, and the convex oculars have similar lines extending over them 

 from their inner side ; the sutures smooth, and without impressions. 



