564 SPATANGINA. 



SPATANGINA. 

 * Subfamily Spatangiua Gkay, 18o5, Cat. Rcc. Ech. 



Spatangoids with a flat test ; petals lanceolate, not sunken, with broad 

 interporiferous spaces flush with the test ; the abactinal part of the poriferous 

 zones usually rudimentary ; a subanal plastron and large interambulacral 

 tubercles within the-peripetalous fasciole (Eupatagus), or in the interambu- 

 lacral spaces. 



The genera of this family, except Eupatagus, have no peripetalous fasciole. 

 On this account Eupatagus has usually been associated with the Brissina, 

 but from the structure of the petals I am more inclined to associate it with 

 the Spatangiua proper. In some genera we have an internal fasciole forming 

 a plastron which is placed above the margin, in the anterior part of the test, 

 and partially obliterates the abactinal part of the anterior poriferous zone 

 of the anterior lateral ambulacra. 



SPATANGUS. 



Spatangus Klein, 1784, Nat, Disp. Ech. 



Test heart-shaped, with broad ambulacra] petals ; poriferous zones alone 

 sunken; odd ambulacrum placed in a more or le<s deep, broad, anterior groove. 

 Large tubercles on the live interambulacral spaces; subanal fasciole very 

 prominent ; no lateral or peripetalous fasciole. 



Spatangus LUtkeni 



: Spatangus Lutkeni A. Ag., 1872, Bull. M. C. Z., III. 



Test thick, distinguished at once by its regularly elliptical outline, in- 

 dented anteriorly by the broad ambulacra] groove ; its test regularly arched, 

 both transversely and longitudinally, truncated at the posterior extremity. 

 The apical system is anterior; the vertex slightly posterior; the outline 

 arching slightly but regularly from the anterior edge to the posterior edge, 

 above the large, broad, elliptical anal system ; the lower surface is much 

 as in S. purpureus, somewhat convex; but the actinal plastron is elongate ; 

 the subanal plastron heart-shaped, about one and a half times as broad as 

 long, while in 8. purpureus it is three times as broad as long, and in S 



* In the List of known species, p. 219, this subfamily is by mistake named Euspati.i^iiia A. Afl. 



