CLEISTOPORA 



59 



by convoluted tubes commonly commencing 

 at mural pores, following random paths not 

 in one general plane, borders in early stages 

 generally not vesicular, in middle adult 

 stages borders may be vesicular on one or 

 more sides, in late stages corallites entirely 

 filled by vesicular matter without reticulate 

 structure; vesicles elongate, approximately 

 parallel with walls grading into reticulate 

 structure; septal crests common. 



Longitudinal sections. — Corallites in- 

 crease regularly in diameter; walls vary 

 rapidly in thickness; vesicles convex up- 

 ward, sloping steeply downward at inner 

 ends; inner reticulate zone diminishing up- 

 ward, replaced entirely by vesicles; septal 

 crests or traces common on vesicles; con- 

 voluted tubes in reticulate zone partitioned 

 by diaphragms. 



Comparison. — This spieces differs from 

 other forms of Cleistopora by its more 

 elongate colonies and its ontogenetic change 

 from reticulate to vesicular structure. 



Occurrence. — Locality 28. 



Material. — Specimens studied, 1. Illinois 

 State Geological Survey No. 3500; holo- 

 type, Rowley collection, not studied. 



Remarks. — Although the structural de- 

 velopment is much different from other 

 species of Cleistopora^ the writer prefers to 

 consider it a specialized member of that 

 genus. Its latest stages are very similar to 

 the typical structure of Pleurodictyum and 

 appear to illustrate the phylogeny of that 

 genus, but its stratigraphic position shows 

 that C. ramosa is not ancestral. 



Cleistopora typa (Winchell) emend. 

 Easton 



Plate 14, figures 1, 2; Plate 16, figures 1-4 



Leptopora typa Winchell, 1863, Acad. Nat. Sci., 

 Philadelphia Proc, p. 3. [in part]. 



Leptopora typa, White, 1880, Contr. Invertebrate 



Paleontology no. 6, p. 122, pi. 34, figs. 12a, 



12b. 

 Lepidopora typa, White, 1880, idem, no. 8, p. 159. 

 Michilinia? placenta White, 1880, idem, no. 8, p. 



157, pi. 39, figs. la-d. 

 Michilinia placenta, White, 1880, idem. no. 8, p. 



159. 

 Leptopora typa. White, 1883, U. S. Geol. and 



Geog. Survey Terr. 12th Ann. Rept., pt. I, 



p. 122, pi. 34, figs. 12a, b. 

 Leptopora gorhyi Miller, 1891, Indiana Dept. 



Geol. Nat. Res. 17th Ann. Rept., p. 6, pi. 



I, figs. 1-4, Adv. Sheets. 



Leptopora gorbyi. Miller, 1892, Indiana Dept. 

 Geol. Nat. Res. 17th Ann. Rept., (1891), pp. 



616-617, pi. I, figs. 1-4. 

 Leptopora typus, Miller, 1892, Indiana Dept. 



Geol. Nat. Res. 17th Ann. Rept., p. 617 



(1891). 

 Cleistopora placenta, Keyes, 1894, Missouri Geol. 



Survey, vol. 4, pt. 1, p. 119, pi. XIV, fig. 11. 

 Cleistopora typa, Keyes, 1894, idem pp. 119, 120. 

 Cleistopora typa?, Keyes and Rowley, 1897, Iowa 



Acad. Sci. Proc, vol. 4, p. 30. 

 Leptopora typa, Weller, 1898, U. S. Geol. Sur- 

 vey Bull. 153, p. 323. 

 Leptopora typa, Weller, 1901, Trans. St. Louis 



Acad. Sci. vol. 11, pp. 194, 195, pi. 20, fig. 19. 

 Leptopora typa, Merrill, 1905, U. S. Nat. Mus. 



Bull. 53, pt. 1, p. 351. 

 Leptopora typa, Robinson, 1917, Connecticut Acad. 



Arts Sci. Trans., vol. 21, p. 164. 

 Leptopora placenta, Robinson, 1917, idem, p. 164. 

 Leptopora gorbyi, Robinson, 1917, idem, p. 164. 

 Leptopora typa. Van Tuyl, 1925, Iowa Geol. Sur- 

 vey, vol. 30, pp. 58, 104, 105, pi. 3, fig. 1. 

 Leptopora typa, Moore, 1927, Am. Assoc. Petrol. 



Geol., Bull, vol. 11, no. 2, p. 1330. 

 Leptopora typa, Moore, 1928, Missouri Bur. Geol. 



Mines, ser. 2, vol. 21, pp. 63, 97, 154, 195. 

 Leptopora typa, Laudon, 1931, Iowa Geol. Survey, 



Ann. Rept. vol. 35, pp. 393, 426, 427, 429, 



(1929). 



Externals. — Corallum thin, subcircular; 

 corallites 5- or 6-sided, very shallow, slightly 

 domed axially; floors granular; epitheca 

 concentrically striate. Diameter of holotype 

 about 4.5 cm; thickness about 3 mm; di- 

 ameter of corallites about 6 mm. 



Transverse section. — ^Walls strong, dense, 

 line of contact between adjacent walls ir- 

 regularly preserved ; nearly straight pores in 

 walls continue into reticulate structure; 

 centers of corallites irregularly reticulate 

 with occasional diaphragms crossing tubules. 



Longitudinal section. — Epitheca thick 

 with faint fibrous structure normal to plane 

 of epitheca; walls merge with internal 

 reticulate structure which tends toward hor- 

 izontality; diaphragms infrequent, domi- 

 nantly vertical. 



Occurrence. — Localities 1, 2, 8, 16, 23, 

 26, 28, 30, 35, 38, 39, 44, 65, 78, 85. 



Material. — Specimens studied, 39. Holo- 

 type, University of Michigan No. 14253; 

 other specimens. University of Missouri 

 Nos. 348, 1049, 1138, Illinois State Geo- 

 logical Survey Nos. 3499, 3507, University 

 of Chicago No. 9764; Miller's figured speci- 

 mens of Leptopora gorbyi are University of 

 Cincinnati No. 3273, whereas the other 



