BEITISH FOSSILS. 



5 



interambulacral rows appear not to extend so far up, and in the 

 ambulacra there are fewer large tubercles developed. 



Var. serialis. — We prefer to apply this name, as Dr. Wright has 

 done, to the depressed variety with pores in close ranks of threes, 

 rather than to our figure 6, which has them oblique. Agassiz's small 

 figure shows close set tubercles in the ambulacral areas, and those 

 two rows are made greatly nearer to each other than to the inter- 

 ambulacral rows, while the pores are described as " no less in ranks 

 of threes than those of U. perlatus." These two characters, the 

 approximate ambulacral rows, and the close ranked pores, agree 

 with specimens from Yerona in the British Museum, and with the 

 larger specimen described by Dr. Wright, as above quoted. This 

 specimen is very evenly covered with granules, and the ambulacral 

 tubercles, more numerous than in the typical variety or in var. 

 germinans, are remarkably irregular in size (see our fig. 5). Some 

 specimens of this variety in the Survey collections are cousiderably 

 more pentagonal than our figure, and have the ambulacral rows 

 wider apart, but have the surface and the pores similar. 



Yar. perlatus. — In the typical variety the form is much inflated, 

 and also moderately elevated. The avenues are broad and not sunk, 

 though the ambulacra project a little. The tubercles are prominent 

 in both areas, and surrounded by conspicuous large granules, inter- 

 mixed with secondary tubercles on both sides of the primaries over 

 a great part of the surface. These become equal in size to the 

 primaries on the under surface, which is therefore crowded with 

 large tubercles. The median line of the interambulacra is bare of 

 granules (but not depressed), and they are occasionally absent down 

 the middle of the convex ambulacra. In one fine specimen in the 

 British Museum, like that figured by Goldfuss as JE. lineatus, the 

 rows of pores are in close threes all the way up ; in another, more 

 elevated, this arrangement alters at the upper third, and the rows 

 become quite as oblique as in our figures 5, 6. The base of K per- 

 latus is convex, more so in depressed specimens, and the angles of 

 the mouth are produced. Not yet found in Britain. 



There is a considerable interval between this variety and the 

 next, but there can be little doubt of their identity as species. 



Yak. germinans. — The difi"erences observable among specimens 

 of this variety are chiefly those due to age (the young being more 

 depressed), and having the pores more oblique ; some of those from 

 the Inferior Oolite, however, are less pentagonal, and with the 

 median line of the interambulacra less depressed, and not so bare 



