126 PROP. p. M. DUNCATf's llEVISIOlSr OF THE 



The interradia have numerous low broad plates, somewhat wavy 

 in sutural outline, depressed near the median line ; two vertical 

 rows of primary tubercles resembling those of the ambulacra, 

 but slightly larger, and two other rows of smaller tubercles which 

 diminish in number remote from the ambitus ; numerous distant 

 large granules. 



Peristome small, sunken ; branchial incisions with rounded edges 

 and rather large. 



Fossil. Eocene: "W. Sind, Asia. 



IX. Family EcHiNiDiE. 



Regular ectobranchiate gnathostomes, having tests with equal 

 diameters, and with horaoiopodous tentacles. Ambulacral plates 

 compound, with three pairs of pores, which are arranged in high 

 or low arcs of triplets. Coronal plates without pits and grooves, 

 and their opposed surfaces plain. Jaws with epiphyses teeth 

 keeled. 



Genus Echinus. 



Subgenus Psammechinus. 

 Genus Stirechinus. 

 Glyptechinus. 

 Leiopedina. 

 Hypechinus. 

 Toxopneustes. 

 Boletia. 

 Genus Tripneustes. 



Subgenus Evechinus. 



Incertse sedis : Prionechinus. 



Genus Echinus, Eondelet, De Pise. Marin. 1554. Lister, 1678, 

 Anim. Ang. p. 169, pi. 8. fig. 18. Linnaeus, 1752-64, Mus. 

 Lud.-TIlr. (pars). Agassiz, 1841, Monogr. d'Ech. viv. etfoss., 

 Pref. to Valentin, Anat. Q-en. Echin. p. 2. Desor, 1858, 

 Synopsis, p. 123. A. Agassiz, 1872-4, Revision, pp. 293 & 489. 

 Loven, 1887, EcJi. descr. hy Linn. pp. 49 & 61. 

 Test varying in size, small, moderate, to very large, tumid at 

 the circular or subpentagonal ambitus, subhemispherical, sub- 

 conical, or tumid dorsally, flat or slightly tumid actinally, tall and 

 short. 



