J. W. Gregory — Australian Echinoidea. 485 



Cardiaster has not hitherto been described except from the 

 Cretaceous. The late Eev. J. E. Tenison-Woods recorded 1 the 

 genus from Mt. Gambier, but gave neither figure nor description ; 

 and, as has been often pointed out, little value can be attached to 

 his generic determination of Echinoidea. The present specimen is 

 somewhat broken, and, as is so often the case in this genus, the 

 fasciole cannot be seen ; nevertheless the general form, the deep 

 anterior groove, and the tuberculation, leave no doubt of its correct 

 generic position. 



The species agrees most closely with the European C. ananchytis, 

 and most nearly with the variety cordiformis. 2 It differs, however, 

 in the greater prominence of the ridges that bound the anterior 

 groove ; the test is higher, the anterior end is steeper, and instead 

 of the gentle slope of the posterior interradium, this forms a 

 horizontal keel, which is terminated abruptly by the almost vertical 

 posterior margin. 



Fam. Spatangid^:. 



Division Prymnadete. 



Genus Pericosmus, Ag., 1847. 



Sp. 1. Pericosmus M'Coyi, sp. nov. 



Pericosmus compressus, M'Coy. Prod. Pal. Victoria, dec. vii. 1882, pp. 21-2, pi. 

 lxvii. fig. 2, and lxviii. (Non Megalaster compressus, Dune.) 



Sp. 2. Pericosmus compressus, Dune. sp. PI. XIV. Fig. 1. 



Megalaster compressus, Dune. Q.J.G.S. 1877, vol. xxxiii. p. 62, fig. 1. 



Prof. Duncan, in 1877, described as Megalaster compressus a large 

 Spatangoid, evidently an ally of Pericosmus, but for which, owing 

 to the absence of fascioles, he instituted a new genus. Prof. M'Coy 

 five years later, in the course of his admirable figures and descriptions 

 of the Victorian Pericosmi, named one species P. compressus, because 

 he was deeply impressed with its resemblance to the specimen 

 described by Dr. Duncan, and with the probability that Megalaster 

 would turn out to be only a badly-preserved representative of this 

 genus. Prof, von Zittel 3 seems previously to have entertained the 

 same doubts, as he only accepted Megalaster with a query. Prof. 

 Duncan, in his " Eevision of the Australian Echinoidea," in 1887, 

 referred to Prof. M'Coy's remarks, and after a brief discussion 

 left the question open. In his recent " Revision of the Echinoidea," 4 

 however, the genus is again quoted without any expression of doubt. 



The question of the retention of the genus Megalaster depends 

 upon whether the absence of fascioles in the type-specimen is due 

 to their never having been developed or to their having been 

 obliterated during weathering. The specimen has certainly been 

 greatly worn ; none of the tubercles on the abactinal surface are 

 shown in Prof. Duncan's drawing, nor are they preserved in the 

 British Museum specimen. It is therefore not surprising that 



1 J. E. Tenison-Woods, Geol. Obs. in South Australia, 1862, p. 77. 



2 Samuel Woodward, Geology of Norfolk, 1833, p. 50, pi. v. fig. 6. 



3 von Zittel, Handbuch der Palaeoutologie, i. 1889, p. 541. 



4 Journ. Linn. Soc. Zool. xxiii. 18S9, pp. 221-2. 



