Info

0.4-0.6 X diam.

' Diameters 1 and 2, longer and shorter diameter of ellipse, respectively.

' Diameters 1 and 2, longer and shorter diameter of ellipse, respectively.

B. Valve outline broadly oval to circular.

Asteromphalus arachne (Brebisson) Ralfs in Pritchard (Plate 25, Table 31) Basionym: Spatangidium arachne Brebisson.

References: Brebisson, 1857, p. 296, Plate 3, Fig. 1; Pritchard, 1861, p. 837, Plate 5, Fig. 66; Hustedt, 1930, p. 493, Fig. 276; Sournia, 1968, p. 25, Plate 9, Fig. 60; Hernandez-Becerril, 1992a, p. 279, Figs. 1-14. Central area eccentric, extremely small. Hyaline rays narrow, the two farthest away from the narrow ray curve away from the valve center.

Asteromphalus elegans Greville (Plate 23, Table 31) References: Greville, 1859b, p. 161, Plate 7, Fig. 6; Sournia, 1968, p. 24, Plate 9, Fig. 59; Hernandez-Becerril, 1991a, p. 17, Plates 16 and 17. Separating lines genuflexed and sometimes once or twice forked. Extension of narrow hyaline ray inside the central area rectangular. Many hyaline rays. Finely areolated sectors, sharply truncated or somewhat pointed toward central area.

Asteromphalus heptactis (Brebisson) Ralfs in Pritchard (Plate 24, Table 31) Basionym: Spatangidium heptactis Brebisson. References: Brebisson, 1857, p. 296, Plate 3, Fig. 2; Pritchard, 1861, p. 838, Plate 8, Fig. 21; Hustedt, 1930, p. 494, Fig. 277; Cupp, 1943, p. 69, Fig. 32; Hendey, 1964, p. 96, Plate 24, Fig. 5; Sournia, 1968, p. 25, Plate 9, Fig. 58; Hernandez-Becerril, 1991a, p. 26, Plates 28 and 29.

Central area small compared to similar species. Separating lines bent or branched. Extension of narrow hyaline line inside the central area almost rectangular. Hyaline rays broad. Areolated sectors coarsely structured, truncated, and narrow (the width of three or four areolae) toward the central area.

Asteromphalus

A. hookeri

A. hyalinus

A. arachne

PLATE 25 Asteromphalus hookeri, A. hyalinus, and A. arachne. Valves with hyaline rays. Scale bar =10 ftm.

Asteromphalus hookeri Ehrenberg (Plate 25, Table 31) References: Ehrenberg, 1844b, p. 200; Ehrenberg, 1844c, Fig. 3; Karsten, 1905, p. 90, Plate 8, Fig. 9; Hustedt, 1958a, p. 127, Figs. 88-90; Hernändez-Becerril, 1991a, p. 23, Plates 24 and 25. Separating lines straight. Extension of narrow hyaline ray rectangular or bell shaped. Areolated sectors wedge shaped and curved toward valve center.

Asteromphalus hyalinus Karsten (Plate 25, Table 31) References: Karsten, 1905, p. 90, Plate 8, Fig. 15; Hustedt, 1958a, p. 128, Figs. 84-87. Small. Central area large and more or less eccentric with convex margins toward wide areolated sectors (six to nine areolae between the hyaline rays). Separating lines genuflexed and branched. Extension of narrow hyaline ray inside central area wide at base with sudden constriction closer to valve center. Hyaline rays few and often slightly curved.

Asteromphalus parvulus Karsten (Plate 23, Table 31) References: Karsten, 1905, p. 90, Plate 8, Fig. 14; Hustedt, 1958a, p. 128, Fig. 91.

Large central area. Separating lines broken. Areolated sectors coarsely structured and convex toward valve center.

Asteromphalus roperianus (Greville) Ralfs in Pritchard (Plate 24, Table 31) Basionym: Asterolampra roperiana Greville.

References: Greville, 1860, p. 120, Plate 4, Fig. 14; Pritchard, 1861, p. 838; Sournia, 1968, p. 26, Plate 9, Fig. 61; Simonsen, 1974, p. 26, Plate 22, Fig. 2; Hernändez-Becerril, 1991a, p. 21, Plates 22 and 23.

TABLE 31 Morphometric Data of Asteromphalus spp. with Broadly Oval to Circular

Valve Outline

Species

Diameter Sector

No. of hyaline rays

Size of central area

A. arachne 40-60 7-8

Was this article helpful?

0 0

Post a comment