FROM THE UPPER WHITE CHALK. 1S5 



■close-set mammillated granules, twenty-six iu each roAV, larger at the base than in the 

 upper part of the area. Within these are two rows of much smaller granules, twenty- 

 two in each, less regular in their arrangement than the marginal rows (fig. 1 (/). The 

 poriferous zones are extremely narrow and the pores disposed in very oblique pairs 

 (fig. Iff), eight lying within the height of one of the large inter-ambulacral plates (fig. 1 i) ; 

 the septum between each pair terminates in a grauuliform elevation (fig. 1 i). 



The inter-ambulacral areas are vi^ell developed (fig. 1 a, d, /), with two rows of 

 tubercles, seven in each ; those in the upper part of the area and at the ambitus are large, 

 and at the base small ; fig. 1 / shows one area magnified four diameters ; the three pairs 

 of large tubercles i^early occupy the entire surface of their respective plates (fig. 1 i) ; the 

 boss has a wide base, surrounded by a well-defined areola, and this is encircled by a 

 series of eight large mammillated granules ; fig. 1 i shows one of these large plates, 

 and fig. 1 i- gives a profile of one tubercle with its surrounding granules, both figures are 

 magnified six diameters ; from the ambitus to the peristome the tubercles gradually 

 diminish in size, and the four small basal nearest the mouth have a row of mammillated 

 granules separating them from the poriferous zones (fig. 1/ and fig. 1 //). The miliary 

 zone is wide, nearly of equal diameter throughout; and in addition to the large granules which 

 form a series of crescents around the areolae the interspace is covered with small granules 

 sparsely strewed over the surface of the plates (fig. 1 d, y, /). The apical disc is 

 large and prominent, consisting of a series of thick plates ; fig. 1 a shows its natural size 

 and I'elations, and fig. 1 i the same magnified four diameters. Three of the ovarial plates 

 have an irregular hexagonal and two a rhomboidal figure (fig. 1 h and e) ; in all the 

 oviductal holes are in the centre of the plates ; the sur-anal plate is much thickened and 

 raised to form the anterior wall of the periprocte (fig. 1 a, h, d, e) ; the ocular plates are 

 triangular, having their base undulated and turned outwards : the outer border of both 

 the ovarial and ocular plates are placed within the circle having its centre at the anterior 

 wall of the vent; the sutures are well marked and punctated with small angular im- 

 pressions ; the vent is large and oblong (fig. 1 b, e), and the periprocte surrounded by a 

 thick prominent annulus, which forms a conspicuous character of the test of this fine 

 Salenia ; the vent is excentral (fig. T a, d), and looks obliquely backwards and to the 

 right side. The base is narrow, and highly ornamented; the small primary inter- 

 ambulacral tubercles are closely set together, and the large mammillated ambulacral 

 granules are very conspicuous, and form a prominent band between the tubercles (fig. 

 1 c, h) ; the miliary zone is wide, and filled with small close-set granules (fig. \f, c). 

 The mouth-opening is oblong (fig. 1 e, /) about one third the diameter of the test. 

 The peristome is decagonal, dividing the opening into ten unequal lobes ; each of the 

 ambulacral lobes, which are the largest, have a double crescentic outHne, fig. 1 h, I -. 

 this is the only species of the genus Salenia which possesses an oblong mouth-opening, 

 and this forms, therefore, one of the specific characters by which it is distinguished from 

 its congeners. 



24 



