140 CYPHOSOMA 



from that species by the late Professor Edward Forbes, and dedicated to N. T. Wetherell, 

 Esq., F.G.S., who presented it to the Museum of the Royal School of Mines. This 

 unique typical example, partly imbedded in flint, was obtained at Gravesend. The test 

 is of moderate size, has a circular figure, and is depressed a little above and below ; the 

 sides are inflated and the base is flat ; the ambulacral areas are wide, with two rows of 

 large tubercles (figs. 1 c, b), nine or ten in each ; the areolae occupy nearly the entire 

 width of the plates, and are bordered by a series of prominent miUary granules, which are 

 absent only on the zonal sides of the plates (figs. 1 e, g, h) \ the tubercles gradually 

 diminish from the ambitus to the oral (fig. 1 ]i) and the discal apertures (fig. 1 g) ; 

 the areolae retain throughout, even to the smallest tubercles, the border of granules special 

 to each (figs, g, h). 



The poriferous zones are much undulated, and form a series of crescents around the 

 large tubercles (fig. 1, d) ; the rows are narrow, the pores simple and unigeminal through- 

 out, and there are from five to six pairs of holes opposite each of the large plates 

 (figs, e, g, h). 



The inter-ambulacral areas, a little wider than the ambulacral, have two rows of 

 primary tubercles, nine in each, and two rows of secondary tubercles placed near the 

 zones, and extending from the peristome to the ambitus (fig. ] c and fig. 1 h). The 

 areolae of the primaries are wide, occupying nearly the whole surface of the plates, and 

 each is bordered by a row of distinct miliary granules (fig. 1 e), which completely separates 

 the areolae from each other. The secondary tubercles are small, and form a short row of 

 twelve tubercles set on bosses ; they occupy a space between the zones and the primary 

 tubercles (figs. 1 c, //), and extend from the peristome to the ambitus. 



The tubercles of both areas are very prominent, and nearly of the same size; the 

 bosses are large, with feebly crenulated sunmiits, closely embracing the mammillou, which 

 is large and conspicuous (figs. 1 e and/). 



The miliary zone is narrow at the ambitus, with two rows of granules ; on the upper 

 surface it becomes wider, depressed, and nude in the middle, and is sparsely supplied 

 there, and at the sides, with very small granules (fig. 1 d). 



The mouth-opening, small and circular, is one third the diameter of the test; 

 the peristome is divided into ten nearly equal-sized lobes, by well defined incisions 

 («g. Ic). 



The discal opening is directly opposite to, and of the same proportional size as the 

 oral aperture; it has a pentagonal form, and the single ovarial plate that extended into 

 the single inter-ambulacrum protruded farther into this area than either the antero- or 

 postero-lateral ovarials (fig. 1 6). 



The upper surface of the test is considerably depressed, and the base is fiat. This 

 contour of the shell is well shown in fig. 1 d. 



Ajfinities and Differences. — This species has the closest affinities with Cyphosoma 

 corollare, of which it may, perhaps, prove to be only a variety. As it is at present a 



