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ECHINOCONUS 



Echinoconus globulus, Desor. PL XLIX, fig. 1 a— g. 



Galerites globulus, Desor. Monographie des Galerites, tab. iv, figs. 1 — 4, p. 18, 



1842: 



— Forbes. In Morris, Catalogue of Brit. Foss., 2nd ed., p. 80 ; 



1854. 



Diagnosis. — Test small, nearly globular ; base narrow ; border rounded ; vent 

 elliptical and supra-marginal; inter-ambulacral plates sparsely covered with primary 

 tubercles. 



Dimensions. — Height, six tenths of an inch ; length, eight tenths ; latitude, seven tenths. 



Description. — The small test figured in our PL XLIX was always considered to be 

 a distinct species by the late Dr. Woodward ; it is identical with the form first described 

 and figured by Professor Desor, in his ' Monograph on the Galerites ; ' the specimen, in 

 fact, which served as the type of Desor's figure belonged to the collection of M. de Luc, 

 who obtained it from the English White Chalk ; at first sight it appears to be a young 

 specimen of E. subrotundus ; a closer examination, however, shows it differs in essential 

 points from that form. The test is slightly elongated, and is nearly globular in conse- 

 quence of the narrowness of the base, and the rounding of the border ; the posterior 

 carina is not prominent, the vent is elliptical and quite supra-marginal, but in conse- 

 quence of the rounding of the border this aperture is visible both from the base and 

 upper surface. The ambulacral areas are built of very narrow plates and have four rows 

 of tubercles arranged obliquely on the area, one tubercle from the inner row alter- 

 nating with a tubercle on the outer row; the poriferous zones are very narrow, the 

 pores unigeminal and oblique, six pairs being opposite one large plate (fig. 1 e). 



The inter-ambulacral areas are twice the width of the ambulacral ; each of the plates 

 supports five or six tubercles arranged in quincuncial order, and the inter-tubercular 

 surface is covered with microscopic miliary granules, of which a capital sketch is given in 

 fig. 1 e ; at the border and base the granules form regular circles around the tubercles, 

 as seen in fig. 1 g. Both these drawings are magnified six diameters. 



The apical disc is large and well developed in this small Urchin (fig. 1 /) ; the right 

 antero-lateral ovarial is the largest plate in the disc and extends into the centre ; it is 

 covered with the spongy body, and the other three ovarials forming the two pairs 

 are small and of the same size ; they are perforated near their apices, and the 

 small posterior single ovarial is imperforate; the five ocular plates are all well 

 perforated. 



The mouth-opening is small and central, and the peristome less in diameter than 

 the supra-marginal elliptical vent. 



Affinities and Differences. —The globular shape of this Urchin resembles some forms 



