50G FIBULARIA. 



FIBULARIA. 



Pibularia Lamk., 181U, An. s. Vert. 



The characters of this genus must remain doubtful, so long as we have no 

 positive evidence that the small species of which it is comjjosed are not the 

 young, either of some species of Echinocyamus or of some species of Cas- 

 siduloids. It contains small species more or less ovoid or flattened, distin- 

 guished from Echinocyamus by the absence of distinct anterior peripheric 

 radiating partitions; there are highly developed auricles, and we find near 

 the anus, on the lower floor, traces of the radiating partitions of Echino- 

 cyamus ; anus infra-marginal. Petals imperfectly petaloid ; diverging pores 

 distinct, not conjugated, or only indistinctly, few in number; petals remain- 

 ing rudimentary, as in young Clypeastroids, and not closing at any time ; 

 poriferous zones extending from the apex to the actinostome as disconnected 

 pores. The jaws are very small, high, resembling in their general structure 

 the jaws of the Echinantliidae. and not of the Scutellidae ; they are inter- 

 mediate in their general features between the jaws of Laganidae and of 

 Echinantliidae. Actinostome central ; anus nearer the actinostome than the 

 ambitus. 



Fibularia australis 



Fibrdaria australis Desml., 1837, Syn. p. 240. 



PL XIII. f. o-io. 



This is the largest species of Fibularia known. Specimens measuring 

 about 20""". longitudinal diameter. ( 10""" transverse,) resemble in general 

 outline small specimens of Clypeaster. The test seen from above is elliptical, 

 slightly broadest anteriorly, regularly arched, with rounded edge from the 

 edge of the test to the apex, which is central ; outline sloping somewhat 

 towards the posterior edge. Petals open at the extremity, diverging from the 

 apex towards the edge of the test ; pores not conjugated ; four genital open- 

 ings ; petals extend nearly to the edge, the posterior pair somewhat shorter ; 

 poriferous zones equal, narrow, but slightly petaloid ; pores distant, round. 

 Mouth large, pentagonal, placed somewhat nearer the posterior edge; anus 

 elliptical, irregularly transverse, very large, occupying a third of the space 

 between the mouth and the posterior edge. Mouth sunken, and the whole 

 median posterior part of the lower side concave, while the anterior and edges 

 are rounded and swollen. Tuberculatum of the abactinal part of the test 



