GENEEA AND aBOUPS OF THE ECHINOIDEA. 201 



Peron, SfGatctJiier, 1879, IJch. Foss. de V Alger. £asc. 5, p. 154, 

 pis. X., xi. De Loriol, 1888, Faune Cret. du Fortug.^ Ech. 

 vol. ii. fasc. 2, p. 83, pi. xv. 



Test moderate or large, thin, ovoid in marginal contour, 

 broadest posterioi'ly, high, subconical at the anteriorly placed 

 and overhauging apex, sloping gradually elsewhere, more or less 

 grooved anteriorly. Actinally plane or convex. 



Apical system at the highest point, with four perforated basal 

 plates. 



Ambulacra diverse, flush ; the odd one non-petaloid, and with 

 a biserial arrangement of small oblique pairs of pores in each 

 poriferous zone ; otber ambulacra short, subpetaloid, tending to 

 close, with diverde pores, the outer elongate ; pores single (?) 

 beyond tbe subpetaloid parts and in high plates, the others in 

 low and broad primaries. 



Interradia broad, and the plates broad, rather low, and nume- 

 rous. Ornamentation of small tubercles and granules. 



Peristome large and widely open, excentric in front, more or 

 less pentagonal, and with a rudimentary fioscelle. Periproct 

 large, ovoid, elongate longitudinally, submarginal. 



Fossil. Cretaceous : Europe, N. Africa. 



G-enus Clatiastee, d'Orbigny, 1855, Fal. Fran^., Ech. Terr. 

 Cret. vol. vi. p. 281, pi. 909. 

 Syn. Archiacia, pars. 



Test of moderate size, inordinately tall, finger-shaped. Apical 

 system at the apex with four basal plates perforated. 



Ambulacra very long, dissimilar, flush; the anterior with single 

 pores in each zone, the other and paired ambulacra with slightly 

 sunken pairs. 



Fossil. Cretaceous : Asia. 



The genus Asterostoma has given much trouble to MM. Cotteau 

 and A. Agassiz. This may be seen by reading M. Cotteau's title 

 of the genus in his Memoir in the Mem. Soc. Geol. de Prance, 

 1871-73, vol. ix. p. 177, and a passage in the Report on the 

 ' Challenger ' Echini, 1881, p. 167. 



It must be admitted that A. Agassiz is quite justified in his 

 remarks about the existence of more than one type in the genus 

 Asterosto77ia as determined by M. Cotteau. 



It is n,.ecessary to differ from M. Cotteau regarding the name 



