FROM THE UPPER GREEN SAND. 167 



Diagnosis. — Test small, globular, upper surface elevated, summit depressed, base flat, 

 sides rounded ; ambulacra narrow, slightly flexed, filled with two rows of granules ; inter- 

 ambulacra wide, two rows, six in each, of well-developed tubercles ; apical disc small, 

 angular, and pentagonal ; diagonal ridges of shell marking the surface of the plates ; base 

 narrow, concave ; mouth-opening small, peristome decagonal with equal lobes. 



Dimensions. — a. The largest specimen, fig. 1 a, altitude half an inch ; latitude six 

 tenths of an inch. 



b. Altitude, three lines ; latitude, five lines. 



c. Altitude, two and a half lines ; latitude, three and a half lines. 



Description. — This beautiful little Urchin, the sole representative of the genus 

 Goniophorus, was at one time not uncommon in the Upper Greensand, near Warminster, 

 and it is curious that no second species of the remarkable group to which it belongs has 

 up to the present time been discovered ; the two other forms which appear in the table 

 of synonyms (G. apiculatus, G. favosus) being only usual varieties of the original type, 

 so beautifully and accurately figured by M. Nicolet in Professor Agassiz's ' Monographies 

 d'Echinodermes/ where it was for the first time described. 



The test is small and nearly globular, the upper surface much elevated, the summit 

 a little depressed, the sides inflated, and the base narrow and flat. The ambulacral 

 areas are very contracted, and slightly flexed (fig. 2 b), the two rows of granules are set so 

 closely together that they alternate on the area ; the poriferous zones are nearly as wide as 

 the ambulacra, the pores are oblique, and the pairs remote from each other, twenty-four in 

 the zone. The inter-ambulacral areas are well developed (fig. 2 a); in the specimen, fig. 

 1 a, there are six primary tubercles in each row, the four above the ambitus are much 

 larger than those on the lower part of the area, and the areola of each tubercle is sur- 

 rounded by a complete circle of small mammillated tubercles (fig. 1 a, d, and fig. 2 a, c) ; 

 the miliary zone separating the two series is narrow and zig-zag, and only a little 

 enlarged at the upper surface (fig. 1 d, fig. 2 a). 



The base is narrow and concave, and the small mouth-opening, one third the diameter 

 of the test, lies in a central depression ; the peristome is divided by feeble incisions into ten 

 equal-sized lobes (fig. 1 c). 



The apical disc (fig. 1 b, d) forms a regular pentagon, ornamented with prominent 

 ridges ; an external carina bounds the outline of the disc, an oval carina encircles the vent, 

 and two others extend from the anterior part of the periprocte to the two anterior sides of 

 the discal pentagon (fig. 2 d), and two others unite these with the sides of the vent (fig. 1 b) ; 

 these ridges of ornamentation have nothing whatever to do with the sutures of the disc, 

 which are very delicate, and only seen in some rare specimens ; these sutures in Gonio- 

 phorus are destitute of the incisions, punctuations, and impressions which form so 

 remarkable a feature in the test of Peltastes. 



The suranal plate lies before the periprocte, having the two anterior carinae passing 

 from the periprocte to the anterior border extended over its surface ; the two anterolateral 



