GENEEA AND GROUPS OP THE ECHITTOIDEA. 87 



Subgenus Lkiosoma, Cotteau Sf Triger, 1859 (genus), Ech. clu 

 Dept. de la SartJie, p. 271 ?, pi. xlv. ; 1881, with Peron et 

 Gauthier, Ech, Foss. de V Alger, pt. 2 of fasc. 8, p. 141, 

 figs. 7-11. 

 Syri. Gomphechinus, Pom. ; Micropeltis, Pom. 

 The primary tubercles are plain, and neither crenulate nor 

 perforate. Pairs of pores biserial throughout, or not so at the 

 ambitus ; several rows of interradial primary tubercles, or two 

 only. 



Fossil. Oolitic : Europe. Cretaceous : Europe and N. Africa. 



Grenus Coptosoma, Desor, 1858, Synopsis, p. 91. Duncan ^ 

 Sladen, 1882-86, Pal. Ind. ser. xiv., Foss. Fch. W. Sind, 

 pp. 116-117, pi. xxii. Duncan, 1885, Quart. Journ. Geol. 

 Soc. vol. xli. p. 447. Lamlert, 1888, Bull. Soc. d. Sci. Nat. 

 de VYonne (extrait), p. 7. 



Syn. Cyphosoma (pars). 



Test moderate, subconical, or depressed dorsally, tumid at the 

 ambitus. Coronal plates few in number. 



Apical system flush, intruding somewhat upon the posterior 

 interradial spaces ; one or more radial plates may enter the sub- 

 circular or deformed periproctal ring ; periproct somewhat thrown 

 back. 



Ambulacra with uniserial pairs of pores, and in arcs throughout ; 

 plates formed of more than three components, uniting after the 

 Cyphosomatoid type. 



Interradia with two vertical rows of primary tubercles, crenu- 

 lated, and with several small secondaries upon each broad and 

 comparatively low plate, larger than or of the same size as the 

 primaries of the ambulacra; sutures may be visible, and the 

 tubercles may be deficient dorsally. 



Peristome moderate to large, with branchial incisions. 



Fossil. Cretaceous : Europe, N. Africa, N. America. Eocene : 

 Europe and Asia. 



Mecent. Japan. 



The genus diff"ers from Cyphosoma ; for it is not diplopodous, 

 and the poriferous plates have more tlian three components. It 

 appears that very probably the recent Phymosoma = Cyphosoma 

 crenulare, A. Ag., and also De Loriol's C. Mortoni, should come 



