PLATE XXni A— Coniiniied. 



Calixjpoka PERELEGANS. 



I'UKO ii. 

 Seo Plato 12. 

 Vif. . 14. An enUM-frement of a portion of the surface of a specimen, showings the form of the cell apertures 

 anii raesopores. (X 18.) 



Lower Held<»rTw>rg' p-oiip. Clarhsville, ff. Y. 

 ^lirfy'h nid iHsqji If'' ' iiiin ni 



Ptilouictva tenuis. 



' '^'  ~ I'agc 39. 

 See Platp« 13 and 17. 

 Fig. 15. An enlarg'ement showing the appearance of the cell apertui-es near the marffin of a specimen. 

 (X IS.) 



Lower Helderlwsrg KTf>"P- tSlinfferlaTid's ereek, near dnrksville, iV. T. 



, , ., StICTOPORA PAPILI.OSA. 



Page 57. 

 See Plate 13. 

 Pig. If. An enlargement showing the form anil arranffemeiit of the papillose cell apertui-es. (X 18.) 

 Lower Helderberg group. Ciarkspille, N. T. 



Stiotopoua ORANATULA. 

 /ItiiUtntifninemafWimin UaMKoittHaqt, Vaga SS. iirwodii insmenrutinn > 



See Plate 11. ,...,.„,,.. 



Fig. 17. An enlargement of a portion of the surface of a specimen, showing thfe'fdrtn and aiTangement of 

 the cell apertui-es, with the thin, slightly elevated granulose peristomes. (X 18.) 

 Lower Helderberg group. CaUkili creek, N. Y. 



RhINODICTYA ? OKANUIXJ.SA. 



Page 40. 



See Plate 17. 



Fig. 18. An enlargement of a portion of a specimen showing the foi-m and arrangementof the cell apertures 



and the numerous gi-annles of the surface. (X 18.) 



Lower Helderberg group. Catskill creek, N. Y. 

 Fig. 19. An enlargement of a portion of a very slender specimen, sho%ving the form and ar-rangement of 

 the cell apertures and the conspicuous granules of the surface. (X 18.) 

 Lower Helderberg group. ClarhivUle, N. Y. 



, ..« .moi 9dj «..iw»,d. Ptilodictva urata. 



>-.Ml)on l«.'>i(io» JaaaJdi"! I ^'"8° **■ 



See Plat« 17. 



Fig. 20. An enlargement of a portion of a specimen, showing the form and ari'angement of the cell aper- 

 tures and the minute triangular pits thin. (X 18.) 



Lower Helderberg group. Sclioharie, N. T. 



StICTOI'ORA ALTERNATA, II. .sp. 

 Fig. 21. An enlargement showing th^ fonm and an-angeniorit of the cell .ipertnif s, and the elevated inter- 

 ai)ertural area. (X 18.) 



Lower Helderberg gi-oup. Clarkgvllle, N. Y. 



.■'■ili-.,n -^■'\'<t"ni\ "irit ni 



—tas rxMi wtdJ-mhi* -. Stiotopora obsoleta. 



Pngo 37. 

 Fig. 22. An enlargement of a portion of a specimen, shdwing the fonn and an'angement of th? c^lj aper 

 tures and the wide non-celluliferous margin. (X 18.) 

 Lower Helderlierg group. C larkavUle, N. Y. 



