The Cretaceous Fauna of Pondolancl. 9,71 



Ambulacra with unigeminal pores in straight vertical rows, but 

 with a slight indication of alternation close to the apex. Pores larger 

 on the upper than on the under surface of the test. Plates com- 

 pound, consisting of three (or occasionally, at the ambitus, four) 

 fused plates. Each plate bears one large, primary, perforate and 

 crenulate tubercle, with small tubercles around the margin. On the 

 base of the test the primary tubercles become smaller, and an 

 additional row of rather large tubercles is seen next to each poriferous 

 zone ; also the smaller tubercles around the primaries are fewer, 

 especially in the middle of the area. 



Interambulacra about twice the width of the ambulacra, with four 

 vertical rows of primary, perforate, and crenulate tubercles similar to 

 those of the ambulacra, and with smaller tubercles around the 

 primary tubercles, forming, in the middle of the area, a fairly 

 broad band. On the base of the test the primary tubercles become 

 smaller and another row of tubercles appears at each margin of the 

 area, and also one or two rows in the middle of the area. The latter 

 take the place of the median band of small tubercles on the upper 

 surface 



Bemarks. — This species is at present known by two imperfect 

 specimens only, one in the Survey Collection, the other in 

 the Hamburg Museum. The latter is the original of Griesbach"s 

 figure, which shows the base of the test, and is somewhat enlarged 

 (x about 11). 



Family CASSIDULID^. 



Genus CASSIDULUS, Lamarck. 



Oassidulus umbonatus, sp. nov. 

 Plate XXXIIL, tigs. 3, 4. 



Description. — Test small, sub-pentagonal, rounded, slightly longer 

 than broad, with the greatest breadth at the beginning of the posterior 

 third. Anterior third rounded ; posterior part somewhat angular. 

 Upper surface convex, depressed or moderately elevated, sloping 

 rapidly to the margins ; posterior end sub-truncate, and slightly 

 produced at the margin. Base concave, with a median longitudinal 

 ridge, which is more prominent behind than in front of the peristome, 

 and becomes angular near the posterior margin. Posterior part of 

 base undulating. 



Apical disc a little in front of the middle, with four genital 

 perforations. 



