254 PEOP. p. M. dttncan's eevision of the 



ferous areas broad and pointed distally, not depressed, and may- 

 be tumid ; poriferous zones broad, closing, more or less sunken ; 

 pores dissimilar. 



Peristome excentric in front, semilunar or subcircular, with 

 a projecting posterior labrum. An ampbisternum bounded by 

 wide ambulacra! areas. Periproct occupying mucb of the pos- 

 terior truncation. A peripetalous fascicle, elliptical and circum- 

 scribiug the petaloid parts of the ambulacra. A subanal fasciole, 

 cordiform or broadly reniform in shape. 



Tuberculation — some large perforated and crenulated scrobi- 

 culate primary tubercles, sparely distributed upon the anterior 

 and lateral interradia, circumscribed by the fasciole ; elsewhere 

 absent ; a small tuberculation, and miliaries largest actinally. 

 Spines short, the largest bent, tufted on the subanal area. 



Fossil. Eocene : Europe, N. Africa, Asia. Miocene : Australia 

 and W. Indies. 



Becent. Australia, N. S. Wales, Arafura Sea, Van Diemen's 

 Land. 



A difficult question has arisen regarding the genus Macro- 

 pneustes, Agassiz, 1847. The genus was founded and the dia- 

 gnosis appeared in Cat. Eais., Ann. Sci. Nat. ser. 3, vol. viii. p. 8, 

 figured in vol. vi., pi. xvi. fig. 2(1846-47). 



Macropneustes Deshayesi was the type, and was supposed to 

 show the generic characters ; but in after years it became evident 

 that the specimen used by Agassiz was worn and useless ; for 

 good ones showed a subanal besides the peripetalous fasciole. 



In the meantime Cotteau had founded Peripneustes for species 

 which were Macropneustes with a subanal fasciole. To add to the 

 confusion, some Macropneustes were described which tallied with 

 the written diagnosis of Agassiz, and had no subanal fasciole. 



No two writers are agreed about the nature of the ambulacra 

 in Macropneustes, whether they are flush or in grooves. 



There is always a desire to retain the genus of an old and valued 

 naturalist ; but it is clear that \i Macropneustes is to be retained, 

 Peripneustes must become its synonym, and the Agassizian genus 

 must be altered. Again, if Macropneustes is altered, the species 

 which tally with the original generic definition must find a home 

 elsewhere. 



Any one who has had the opportunity of studying the method 



