FROM THE GREY CHALK. 177 



by the numerous small close-set tubercles of the inter-ambulacra, the large granules of 

 the ambulacra, and the width of the miliary zones. The mouth-opening is large, more than 

 one third the diameter of the test ; the peristome is deeply incised, and forms ten nearly 

 equal-sized lobes (fig. 1 b). 



The apical disc is small and thick, and rises above the test (fig. 1 c and d). The 

 two antero-lateral and the left postero-lateral plates have a rhomboidal figure, and 

 are nearly the same size. The right postero-lateral, the single plate, and the suranal are 

 small in consequence of the encroachment of the vent ; the posterior border of the 

 suranal is thickened and elevated (fig. 1 c, d, i), and rises to form the anterior wall 

 of the periprocte ; the sutures between the three anterior ovarial plates are each 

 marked by six deep punctuations, which define their line of junction ; and the sutures, 

 uniting the ocular with the ovarial plates, have each three deep punctuations (fig. 1 c and 

 fig. 1 i). The test I have figured has not the perforations in the ovarial sutures as distinctly 

 marked as the test which now lies before me for description, so that this character varies 

 in different specimens. The vent is round and elevated, and placed near the posterior 

 part of the disc (fig. 1 c). The periprocte projects upward and backward (fig. 1 a and (/), 

 and forms a crenulated rim around the aperture (fig. 1 a, fig. 1 d, and fig. 1 i). 



Affinities and Differences. — In a large majority of specimens the general form of the 

 body in 8. Austeni differs from S. j)etaUfera in being more globose and elevated. The 

 apical disc is smaller in diameter, and thicker in substance. The vent is likewise more 

 elevated, the periprocte more produced, and its margin sharply crenulated. In the 

 structure of the areas, such as the character of the granules in the ambulacra, and the 

 tubercles in the inter-ambulacra, there is a close resemblance between these portions of 

 the test in both species. 



Locality and Stratigraphical Position. — S. Austeni is the most abundant species in 

 the Lower or Grey Chalk, near Folkestone ; from this locahty and stratum it has been 

 collected by my kind friend, the Rev. T. Wiltshire, F.G.S., to whom I am indebted for 

 several fine specimens given to help me in my work. 



History. — Named by the late Professor Edward Forbes, but not described by him. 

 A brief diagnosis of the species was given by my late friend Dr. Woodward, in the 

 Appendix to the Fifth Decade of the ' Memoirs of the Geological Survey.' It is now figured 

 and described in detail for the first time. 



Salenia Clarkii, Forbes. PL XXXVIII, fig. 1 ; PI. XXXIX, fig. 1 ; PI. XLII, 



figs. 1, 2, 5. 



Salenia Clarkii, Forbes. In Morris's Catalogue of British Fossils, p. 89, 1856. 

 — — Woodward. Mem. Geol. Surv., Decade V, App., p. 5, 1856. 



Diagnosis. — Test globose, elevated, flattened on the upper and under surfaces; 



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