PLATE XXin— Oontinaed. 

 TkEMATOI'OKA (OkTIIOPOKa) nodosa, II. SI). 



Fi^. 10. An enlargement showinf<f the form and arrangement of the cell apertures, their slightly elevated 

 margins and the pi-ominent nodes. (X 18«) 



Lower Helderberg grouji. Clarksville, N. Y. 



Trematopoba (Outhopora) hiiombifkra. 



Pasre 18. 

 See Plate 11. 

 Fig. 11. An enlargement of a s[)ecimen, the sni-face of which has been somewhat weathei-ed. 



Lower Helderberg group, ('lur/civille, N. T. 

 Fig. 12. An enlargement showing pi-ominent nodes at the angles of the vestibular arua«. 

 Lower Helderberg gi-oiip. ClarlisvWc, N. Y. 



Callopoka (Callotrypa) striata. 



Page 26. 

 See Plate 11. 

 Fig. 13. An enlargemeift showing the fonn and airivngement of the cell apertures, the prominent node at 

 the base of each aperture, and the mesopores so arranged that their margins have the appear- 

 ance of longitudinal striations. (X 18.) 



Lower Helderberg group. Schoharie, N. T. 

 Fig. 14. An enlargement showing the cell apertuies with slightly elevated margins, without nodes. The 

 mesopores appear simply as interrupted stnations. (X 18.) 

 Lower Heldei-berg group. Schoharie, N. Y. 

 -•t*l« Ilao sdJ ^o ti\r<in->vi\i:ru. i ,. , :t 



Callopora (Callotrypa) macropora. 



Page 24. 



See Plate 11. 



Fig. 15. An enlargement showing the oval cell apertures with their equally elevated margins, which are 



frequently in contact. (X 18.) 

 li-.il) .<-.•■•(■, Lower Helderberg group. Clarksville, K. Y. .i',| 



Fig. 16. An enlargement showing cell apertui-es without elevated margins. The sui-face between the 

 apertures is elevated, angular and with few mesopores. 

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

 Fijj. 17. An enlargement showing the margins of the cell apertures distinctly and equally elevated and 

 with two or three ranges of mesopores between adjacent cell apertures. (X 18.) 

 Lower Helderberg group. Slingerland's Creek near Clarksville, N. Y. 

 Fig 18. An enlargement showing the cell ajjertures without elevated margings. Interapertural space 

 elevated, rounded and with moderately pi-ominent nodes. Mesopoi-es few and often obsolete 

 over a poHion of the specimen. 



Lower Helderberg group. Clarksville, N. Y. 

 Fig. 19. An enlargement showing the cell apertui'ea polygonal in form, fi-om mutal pressure and vrith con- 

 spicuous mesopores. The peristomes ai-e thin and sti-ongly and equally elevated. (X 18.) 

 Lower Helderberg group. Clarksville, N. Y. 



''"' ''"Trematopoba ? (Trematella ?) corticosa."'"'"'^'"'" ^■' 



Page 15. • r i o mr 



See Plates 10 and 13. M^fnaoA .8 .„« 



Fig. 30. An enlargement showing regularly oval cell apertures. (X 18.) 

 Lower Helderberg group. Clarksville, N. Y. 



Callopora (Callotrypa) paucipora, n. sp. 



Fig. 21. An enlargement showing the form iind .•iiTJiiitri'raent of the cell apertures, thescattered mesopoi-es 

 and nodes. n--M ii"'- l.ci-. i,.-,. ijiiiro iiA .'.' .-aiA 



Lower Helderbeiif group. CLarksvQle, N.T. 



