AULACO DISCUS. 



487 



Valves disciform, with cellular or granular structure, without a 

 median area, furnished with 1 to 4 processes, which are not connected 

 with one another by costae or sulci. Girdle face rather narrow. 



The genus includes about 15 species, only one of which belongs to our 

 coasts, E. Argus (fig. 222), which Mr. Rattray ranks among the Aulacodiscus. 

 I find the structure much too peculiar to rank in that genus, and I shall 

 therefore preserve it here. A certain number of the Eupodiscus are fossil. 

 They are found in the Barbadoes deposits. Others again are found living, 

 and belong especially to warmer regions than ours. 



E. ArgUS Ehr. (Kreideth, p. 77, No. 60; H.V.H. Atl., pi. 117, f. 

 3-6*; Type No. 508), plate 21, fig. 647. 



Valve orbicular, convex, furnished with 3 to 5 rather robust processes, 

 inflated at the apices; formed of two very different layers; the superior 

 with coarse irregular alveoles with openings from above, the inferior with 

 puncta arranged in radiating rows. Girdle face with convex margins; con- 

 necting zone showing some transverse plica? and longitudinal stria?, punctate, 

 delicate, about iS to 20 in 1 c.d.m. Diameter of valve, 8 to 20 c.d.m. 



Marine. Blankenberghe, Ostend, Antwerp (Scheldt), and on all the coasts of the North Sea. 

 England (Shadbolt, Kitton, Stolt., Norman). Ireland (O'Meara). 



E. commutatus Grev. and E. < J f o?iesia>u/s Grev. are only forms of 

 Coscinodiscus concinnus, a description of which will be found in a later page. 



GENUS 149. AULACODISCUS EHR., 1845. 



Valves generally cir- 

 cular, granular, furnished 

 with processes, variable 

 in number, connected 

 with oneanotherthrough 

 the centre, either by a 

 sulcus or by costal, or by 

 granules arranged in 

 special lines 



This genus includes a 

 considerable number of 

 forms almost all remarkable 

 for their beauty, as may be 

 seen from figure 223, which 

 represents A. orienta/is 

 Grev., after Ad. Schmidt. > 



Fig. 223. - Aulacodiscus orientalis. 



