CORALS AND BRYOZOA. 79 



sometimes entirely covered by an organic deposit, and presenting a pustuli- 

 form aspect. 



This species can be easily distinguished by the numerous, conspicuous, sub- 

 stellate maculae. 



Formation and locality. Upper Helderberg group, Falls of the Ohio river. 



LiCHENALIA BISTRIATA. 



PLATE XXXn, FIGS. 6-14. 



Lichetialia Hstriaia, Hall. 'I'rans. Albany Institute, vol. x, abstract, \i. 8. 1881. 



Repoi t of State Geologist for 1885. Expl. pi. 23, figs. 6-14. 1887. 



ZoARiCM lamellate, free or encrusting. Cell tubes without septa. Apertures 

 lunate or semi-circular, diameter .40 mm. Anterior portion of the peristomes 

 very slightly elevated ; posterior portion strongly elevated, projecting over and 

 partially concealing the opening, which is margined by two slight denticula- 

 tions. When the surface is worn or macerated the elevated margins become 

 obsolete, the apertures appearing simply as lunate or semi-circular openings. 

 Surface with slightly elevated maculaB, the centers of which are without cell 

 apertures, the apertures adjacent to these radiate from them and are more 

 oblique than the others. Intercellular space septate. 



This species resembles L. lunata, but may be distinguished by the strongly 

 elevated cell margins, and the absence of septa in the cell tubes. 



Formation and locality. Upper Helderberg group, Falls of the Ohio river. 



LiCHENALIA GEOMETBICA. 



PLATE XXXII, FIGS. 21-23. 



lAchenalia gtometrica. Hall. Report of State Geolo^st for 1885. Expl. pi. 32, figs. 21-23. 1887. 



ZoABiUM consisting of very thin lamellate expansions, incrusting other objects. 

 Cell apertures oblique, sub-triangular, diameter .30 mm.; irregularly dis- 

 posed ; posterior margin very strongly elevated, oblique, angular. Surface 

 with maculae, the centers of which are distant from each other about 5 mm. ; 

 the cells immediately adjacent and radiating from them, are larger and more 



