58 P. M. DUNCAJST ON THE ECHINODEPwMATA OP THE 



Considering that the abortion of the anterior poriferous zone of 

 the antero-lateral ambulacra has been so often figured in Hemipatagus, 

 it is remarkable that a more strict search after an internal fasciole, 

 which could alone produce that peculiarity, has not been previously 

 successful. The best'Mordialloc specimens indicated it perfectly; 

 and many old and worn specimens give indications of its presence 

 now that one knows where to look for it. The subanal linear 

 fasciole is situated just where the posterior and truncated (actinal) 

 part of the test touches the surface on which the test rests ; hence 

 it is readily worn off, after the spines have been removed, by the 

 ordinary attrition to which fossils are subject. 



Some confusion has arisen in the nomenclature and in the specific 

 distinction of the Australian Hemipatagi (now Lovenice) already 

 known, owing to my communication to the Ann. and Mag. Nat. 

 Hist., ser. 3, vol. xiv. Sept. 1864, having been overlooked by Laube, 

 whose admirable essay on the Fossil Echinida of the Murray cliffs 

 was read before the Vienna Academy in 1869. He redescribed the 

 same species which I had called Hemipatagns Forbesi, Woods and 

 Duncan. In 1875 Mr. R. Etheridge, jun., described in the Quart. 

 Journ. Geol. Soc. vol. xxxi. No. 123, p. 445, a species which he has 

 called H Woodsi, and in order to define it from H. Forbesi had the 

 latter figured in outline giving a side view. This figure does not 

 correspond with mine in Ann. and Mag. Nat. Hist. ser. 3, vol. xiv. 

 plate vi. fig. 3 ; nor does it with Laube's. Again, my figure and 

 Laube's are not exactly alike ; for a certain amount of variation 

 must be conceded to all the species of this genus ; and the figure in 

 the ' Sitzungsberichte ' has a more truncated and less depressed 

 anterior front test than mine. Mr. Etheridge's figure is shorter 

 and more truncated still, and approximates to his new species H. 

 Woodsi, so as in fact to restrict the specific diagnosis to the greater 

 or less number of large tubercles with sunken scrobicules in the two 

 lateral interambulacral spaces on either side. 



Laube evidently had better specimens than those from which 1 

 described H. Forbesi. It appears, after an examination of a nume- 

 rous series (35 to 40) of Hemipatagi from the Australian Tertiaries, 

 that there are groups embraced under the species H. Woodsi audi/. 

 Forbesi, Etheridge ; but they are connected by intermediate forms. 

 There are H. Woodsi, with flat and with truncate ends, with oval 

 or transversely elongated periprocts, with numerous tubercles in 

 the lateral interambulacra or with few. The larger H. Forbesi 

 resemble the H. Woodsi in shape, and have variable numbers of 

 tubercles ; and the number even differs on the opposite sides of the 

 same individual. 



The depth of the anterior furrow, the distinctness of the subanal 

 fasciole, and the width of the ornamentation included by the in- 

 ternal fasciole vary in specimens possessing perfect resemblunces 

 in other structures. The number of pairs of pores in the ambulacra 

 is, in the majority of the specimens, as follows (taking 15 as good 

 types) : — 



