70 PEOF. p, M. Duncan's revision or the 



above, depressed and subpulvinate actinally. Apical system 

 wanting, large. 



Ambulacra with two vertical rows of small, imperforate, cre- 

 nulate, primary tubercles ; poriferous zones straight, the pairs 

 biserial to below the ambitus, in barely oblique triple combina- 

 tions, not increasing near the peristome. 



Interradia with abactinal bare median areas, broad, with two 

 vertical rows of small distant primary tubercles resembling the 

 ambulacral, with large bosses and small mamelons, all diminishing 

 abactinally, scrobiculate ; small crenulated secondaries between 

 the primaries and the poriferous zones; granules abundant 

 around the tubercles. 



Peristome sunken, subcircular. Spines slender, elongate, 

 cylindrical, marked throughout with granular costse, which are 

 regularly placed ; the ring is crenulated. 



Fossil. Upper Cretaceous : Europe. 



Grenus Diplotagma, ScJililter, 1871, Zeitsch. f. d. ges. Natunv. 

 (Giehel), n. Y., Bd. iv. p. 339. Zittel, 1879, FaUontol. 

 Bd. i. Lief. iii. p. 509. 



Test thick, high, conical, spheroidal. 



Apical system small, with a narrow ring. 



Ambulacra broad; pairs of pores biserial, and with from five 

 to eight pairs to each tubercle-bearing plate ; plates compound. 

 Tubercles similar in both areas, plain, numerous. 



Peristome small, central ; branchial incisions small. 



Fossil. Cretaceous : Europe. 



Grenus Miceoptga, A. Agassiz, 1879, Froc. Amer. Acad. vol. xiv. 

 p. 200 ; Report on ''Challenger ' Fcliini, 1881, p. 67. Duncan, 

 1885, Journ. Linn. Soc. (Zool.), vol. xix. p. 110, pi. 5. fig. 11. 



Test large, thin, flat actinally, with a rather sharp circular or 

 subpeutagonal ambitus, arched upwards towards the low flattened 

 abactinal surface, broader than high. 



Apical system central, with a small periproct, its membrane 

 with small plates, with miliaries ; anal opening minute. Basals 

 uniform, largely perforate, angular towards the interradia. Madre- 

 porite in the usual basal. Eadial plates all entering the narrow 

 periproctal ring, concave at the distal edge where the pore is 

 situate. 



