502 SYSTEMATIC PALEONTOLOGY 



Genus HYALODISCUS Ehrenberg. 



Hyalodiscus laevis Ehrenberg. 



Hy'ALOdiscus stelliger Bailey. 



Genus ACTINOCYCLUS Ehrenberg. 



Actinocyclus ehrenbergii Ealfs. 



Acting GYGLus ellipticus Grunow. 



Plate CXXXIV, Fig. 1. 



Actinocyclus ellipticits Van Heurck, 1881, Syn. Diat. Belg., pL csxiv, flg. 10. 

 Actinocyclus ellipticus Rattray, 1890, Jour. Quekett Club, ser. ii, voL iv, p. 192. 



Description. — Valve rhombic-elliptical. Markings granular, 6 in .01 

 mm., irregular at the center and radiating toward the border where they 

 are about 12 in .01 mm. Apiculi at irregular intervals. Pseudo-nodule 

 small at or near the end of minor diameter. Diam. .066 mm. Smaller 

 end with more minute markings than Coscino discus lewisianus for which 

 it might be mistaken. 



Occurrence. — Calvert Formation. 1 mile north of Jones Point., 

 Marriott Hill. (Not common). 



Collection. — Maryland Geological Survey. 



Actinocyclus facisculatus Castracane. 



Actinocyclus marylandicus Eattray. 



Actinocyclus moniliformis Ealfs. 



Plate CXXXIV, Fig. 2. 



Actinocyclus moniliformis Ralfs, 1861, Pritchard's Infusoria, p. 834. 

 Actinocyclus ehrenbergii Ralfs var. {fide Rattray). 



Actinocyclus moniliformis Schmidt, 1874, Diat. Nordsee, pi. ill, tig. 31. 

 Actinocyclus moniliformis Van Heurck, 1881, Syn. Diat. Belg., pi. cxxiv, flg. 9; pi. 



cxxv, fig. 1. 

 Actinocyclus moniliformis Rattray, 1890, Jour. Quekett Club, ser. ii, vol. iv, p. 182. 



Description. — Valve circular with striated border. Markings rounded 

 in fasciculate rows, separated by hyaline lines showing more crowded 

 near the circumference where the shorter rows are parallel. Central 

 space rounded with a few scattered granules. Pseudo-nodule distinct. 

 Apiculi opposite the hyaline spaces along each of which extends a single 

 row of markings. 



This form is by some authors united to A. ehrenbergii into which it 

 passes by intermediate forms, and from which it differs chiefly in the less 



