66 p. M. DUNCAN ON THE ECHINODERMATA OP THE 



ambitus in the ambulacral areas, and there is some variation re- 

 garding the position of the periproct. This is not always supra- 

 marginal, but may be marginal and even inframarginal, all the 

 other attributes of the species being present. The other species I 

 have described, Arachnoides elongatus, links on the form described 

 by Laube as a Monostychia, which I believe to be a true species of 

 this genus Arachnoides. 



Echinolampas ovuLUM, Laube. 



This species is distinct from the modern Echinolampas oviformis, 

 Gray, which is found in the Red Sea and Molucca seas. The genus 

 has other recent species in the Florida sea and off the west coast 

 of Africa. The fossil forms are principally Nummulitic in age ; but 

 some are found in the other Tertiaries. The Hala range yields 

 several species ; and thus Echinolampas was very much in its proper 

 area when it was living in the old Australian seas. Like most other 

 forms with a great vertical range, it has a large horizontal one. 



Rhynchopygtts dysasteroides, nobis. 



This species has some very remarkable secondary peculiarities 

 which resemble in their curious nature the many Australian oddities 

 of structure of forms of genera of worldwide distribution. The 

 form has all the generic peculiarities of JRhynchopygus ; but its 

 generative pairs of pores are widely apart. It has an elongated 

 apical system ; and this Dysasterian peculiarity recalls the genera 

 Hyboclypus and Holectypus. The genus has a wide range in time, 

 for it is represented in strata belonging to the Gault; and in space, 

 for the recent forms are found in the Atlantic and Pacific seas of 

 America. 



ECHINOBEISSUS AUSTRALIA, nobis. 



This species is known at once by the elliptical outline of the 

 ambitus, the faintly projecting ambulacra, and the small size of the 

 tuberculation. It differs from Echinobrissus recens, Edw. (called 

 usually Nucleolites recens), a recent species from Madagascar and 

 New Zealand ; for this has longer petals, round pores, flush ambu- 

 lacra, a longitudinally elliptical anal furrow with a posterior edge 

 nearly on a level with the edge of the test, and a large tubercula- 

 tion. It is distinguished from Echinobrisssus (Nucleolites) epigonus, 

 Mart., of the seas washing the East-India Islands, in which the 

 actinosome is elongated longitudinally. Both of these recent forms, 

 however, are closely allied to the Australian fossil species. There 

 is a fossil species of this genus called Nucleolites pajnllosus, Zitt., 

 from the Tertiary beds of the "Waikato river in New Zealand ; but 

 it is distinct from the Australian species (Zittel, Foss. Moll, und 

 Echinod. aus Neuseeland, p. 62). 



The old genus Nucleolites contained many forms which rendered 

 its being broken up into others necessary ; but the writings of 

 Wright, Desor, and A. Agassiz show how unsatisfactory the present 

 and the past classifications have been. The genus was formerly 

 considered to belong to the Secondary ages of the world's history ; 



