FAMILY 7. AMMODISCIDAE 99 



Subfamily 1. Ammodiscinae 

 Test free 



Genus AMMODISCUS Reuss, 1861 



Plate 9, figures 1-4 

 t 

 Genotype, by designation, Operculina incerta d'Orbigny 



Am.modisciis Reuss, Sitz. Akad. Wiss. Wien, vol. 44, 1861, p. 365. 

 Operculina (part) d'Orbigny, in De la Sagra, Hist. Fis. Pol. Nat. Cuba, 



1839, p. 49, 

 Orhis Strickland, Quart. Journ. Geol. Soc, vol. 2, 1848, p. 30 (not Orhis 



Philipps). 

 Spirillina Williamson, Rec. Foram. Great Britain, 1858, p. 93 (not 



Spirillina Ehrenberg, 1841). 

 Trochatnmina (part) of authors. 

 Cornuspira (part) of authors. 

 Involutina (part), Terquem, Mem. Acad. Imp. Metz, 1860-61 (1862), p. 



450. 



Test free, planispiral, with a proloculum and long tubular un- 

 divided second chamber, coiled regularly in one plane ; wall finely 

 arenaceous with a large proportion of yellowish- or reddish- 

 brown cement, surface smooth ; aperture formed by the open end 

 of the chamber. 



Silurian to Recent. Recent species widely distributed, most 

 abundant in colder and deeper waters, but occasionally in warm 

 shallow water. Specimens are very abundant in the Pennsyl- 

 vanian. 



Genus HEMIDISCUS Schellwien, 1898 

 Plate 9, figures 8-10 



Genoholotype, Hemidiscus carnicus Schellwien 

 Hemidisciis Schellwien, Palaeontographica, vol. 44, 1898, p. 266. 



Test with proloculum and long tubular unbranched second 

 chamber, the early chambers planispirally coiled, later ones 

 becoming more or less involute on one face ; wall arenaceous with 

 much cement; aperture formed by the open end of the tubular 

 chamber. 



Carboniferous to Recent. Europe and America, Mediter- 

 ranean. 



