FROM THE INFERIOR OOLITE. 177 



Description. — I only know two fragments of this remarkable Pedina, the one (fig. 2 a) 

 was collected by the late Dr. William Smith from the Inferior Oolite at Tucking 

 Mill, the other (fig. 2 c) I found in the Inferior Oolite, near Birdlip. The description 

 given by Dr. William Smith of this species was the following : 



" Pentangular, depressed, with projecting and rather distant small mamilla? ; two 

 contiguous rows in each areola, and four converging rows in each area, the two 

 middle rows short, and only on the side or widest part of the area ; rough, with 

 small points encircling the mamillse ; rays obliquely triporous. 



" The areolse form the angles of the pentagon. The two larger rows of mamillse 

 in each area are parallel to the rays, and converge to the aperture, and the space 

 between them on the side is occupied by two shorter converging rows. 



" Locality.— Tucking Mill." 



Dr. Smith's specimen is a fragment (fig. 2 a) which exhibits a part of two inter- 

 ambulacral and an ambulacral area, the upper surface is concealed, and only two of 

 the notches of the peristome are exposed ; the other specimen (fig. 2 c) is smaller, 

 but shows more of the form and structure of the test. The ambulacral areas are narrow 

 and straight ; their two rows of tubercles, which are nearly as large as those of the 

 inter-ambulacra, closely alternate (fig. 2 b) between the peristome and the circumference, 

 but as suddenly disappear from the upper part of the area (fig. 2 c). 



The poriferous zones are wide, extremely so below (fig. 2 a), where the trigeminal 

 ranks lie at angles of from 15° to 45° (fig. 2 b), above the ranks are more oblique, and 

 wider apart, but throughout, the pores are always arranged in triple oblique pairs. 



The inter-ambulacral areas are upwards of three times the width of the ambulacral ; 

 from the peristome to the equator each of the inter-ambulacral plates has two tubercles 

 developed on its surface (fig. 2 b), the primaries occupy the zonal sides of the plates, and 

 the secondaries their outer margin ; the primary tubercles, nine or ten in each row, 

 are raised on very prominent bosses (fig. 2 b), encircled by smooth well-defined areolas, 

 around which circles of small granules are disposed (fig. 2 b); as the tubercles are placed 

 very near the ambulacra, and the secondaries are absent on the upper surface, there is 

 an unusually wide miliary zone in this region of the test, which is filled with numerous 

 small granules, among which some minute perforated tubercles are interspersed (fig. 2 b). 



The upper surface of the specimen (fig. 2 d) is covered with an extremely hard 

 rock, that of fig. 2 c shows the opening for the apical disc, which is of moderate 

 width. Only two of the notches of one angle of the mouth (fig. 2 a) are exposed; they 

 are deep, and have reflected edges; the peristome is unequally lobed, and those of the 

 ambulacra are much the largest. 



Affinities and differences. — The only urchin which this species resembles is Hemipedina 

 Bakeri, PL X, fig. 1 ; the mode in which the tubercles closely alternate in the ambulacra, 

 and the proximity of the primary tubercles to the poriferous zones, show the near 



