146 PEor. p. M. dtjitcan's eeyision op the 



minute pores occupy the transverse sutures of the plates aetinally, 

 and some are in the vertical sutures between the ambulacral and 

 interradial plates. Interradial areas supported internally by a 

 pair of strong, complex, vertical partitions, and the other parts 

 of the test, within, bristle w^ith projections. 



Peristome central, sunken or not. Periproct actinal, between 

 the peristome and the posterior margin. Tuberculation minute. 



Fossil. Eocene : Europe, Africa, and Asia. Miocene : Europe. 



A good series of drawings of a Sismondia will be found, by 

 Sladen and Foord, in Monogr. Foss. Ech. Sind, pt. iii. pi. xxv., Pal. 

 Ind. ser. xiv. 1884. They may be compared with the drawings 

 of two species of FcJiinocyatnus which are upon the same plate. 

 The Sismondia differs in the more definite plating of the apical 

 disk and the longer and more shapef ul ambulacra, which are, more- 

 over, tumid. But the alliance is very close. It will be observed 

 that there are several additions to the diagnosis of Desor, in the 

 above definition. 



Genus Fibtjlaeia, Lamk. 1816, Hist. Nat. Anion, s. Vert. vol. iii. 

 p. 17. Gray, 1855, Catal. Bee. Ech. Brit. Mus. pt. i. 

 p. 28. A. Agassiz, 1873, Bevision, p. 506. 



Syn. Ilortonia, Gray {non Desor). 



Test small, thin, ovoid or elongate-elliptical, regularly arched 

 and tumid dorsally, or subspherical, tumid at the sides and aeti- 

 nally around the sunken peristome and periproct. 



Apical system central ; four genital pores. 



Ambulacra short, with ill-developed, very open petaloid parts ; 

 pairs of pores very few, continued wide apart to the margin, not 

 united by a groove. 



Interradia with or without the middle of the plates being 

 raised. 



Peristome small, pentagonal, sunken. Minute concentric 

 plates in the peristomial membrane. Jaws high, stout or slender; 

 teeth superior, sloping ; perignathic processes large. Periproct 

 actinal, sunken, nearer the peristome than the posterior margin, 

 may be longitudinal and oblong. Internal structure of the test 

 very simple, supports very rudimentary or absent, limiting the 

 ambulacra near the edge. Tuberculation distinct, regular, or 

 more distant aetinally. 



Fossil. Upper Cretaceous : Europe. 



