Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/96

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 ;