FROM THE CORALLINE OOLITE. 383 



crushed or have been much injured in cleaning; fortunately I have obtained two 

 good examples, which have been beautifully figured in PI. XXXIV, one of these 

 specimens was obtained from a band of clay and has the form and sculpture finely 

 preserved. 



The thin test has an oblong form, rounded before, dilated in the middle, and 

 a little rostrated behind (fig. 1 a) ; the upper surface is uniformly convex (fig. 1 c) ; 

 the sides decline equally towards the border (fig. 1 d), which is rather attenuated ; when 

 the shell is viewed in profile, the margin is seen to be much undulated (fig. 1 c, d). 



The ambulacral areas taper gradually from the border to the disc (fig. i a), and lie on 

 the same plane with the general surface of the test ; the poriferous zones on the dorsal 

 surface are petalloid for three fourths of the space between the border and disc, they he 

 rather beneath the general plane of the test, and form very uniform graceful petals on the 

 upper surface, narrow below, gradually swelling out in the middle, and tapering to narrow 

 lanceolate terminations at the disc (fig. 1 a) ; the pores of the inner row are round (fig. 1 

 e), those of the outer row in the form of long, narrow, transverse slits ; the pores of 

 both rows are conjugate through fine sulci; there are eight pairs of pores opposite 

 one of the large plates, and a septum between each transverse slit, the outer surface 

 of which supports a regular row of fine granules (fig. 1 e). 



At the lower fourth of the areas the pores lie close together, the rows are here very 

 narrovi', and continue so across the base, the pairs of pores in this region, being placed at 

 wider distances apart (fig. 1 b), near the mouth-opening they lie closer together in triple 

 oblique rows in the penta-phylloid floscelles of the ambulacra, which radiate outwards 

 between the lobes in depressions of the test (fig 1 b). 



The inter-ambulacral areas are of unequal width ; the antero-lateral pair are the 

 narrowest, and the postero-lateral pair, and single area, are of the same Avidth, but broader 

 than the anterior pair ; their surface is marked by two slight ridges, which radiate from 

 the disc to the border, and subdivide each area into three segments. In specimens which 

 have been scraped or filed, unfortunately almost universally the case with this Clypeus, 

 these ridges are not seen ; but in the small, nearly perfect specimen (fig. 1 c, d), they form 

 a very prominent character in its upper surface, and which is faintly represented in fig. 1 a 

 in the left antero-lateral segment. The inter-ambulacral ridges form distinct prominences 

 at the border, and on the surface of the basal cushions ; the_y likewise form two 

 small carina3 on the deflected basal surface of the small specimen (fig. 1 d). The small 

 tubercles are arranged in rows with great regularity on the plates, of these there are in 

 general four on each ; the tubercles are surrounded by sunken areolas, and the inter- 

 mediate surface is covered with rather large granules (fig. 1 /), which give a highly 

 ornamented sculptured surface to the test, when examined with an inch lens. The 

 tubercles at the base are very much larger than those on the upper surface ; some of them 

 likewise are perforated, especially those situated in the concave depression in the vicinity 

 of the mouth (fig. If). 



50 



