52 



CHOUTEAU CORALS 



Survey collection but ft is not available and 

 perhaps is lost. Specimens examined, Univer- 

 sity of Missouri No. 7209, not numbered. 



Remarks. — The fossula is indistinct in 

 most sections, but is recognizable. Interest- 

 ing features in the coral are the rather 

 coarse thick dissepiments and the progressive 

 weakening and ultimate disappearance of 

 the axial structure. The species seems closely 

 related to Koninckophyllujn tortuosum 

 (IVIichelin) from the Tournaisian. 



Genus Vesiculophyllum Easton n. gen. 



Diagnosis. — Simple, straight to curved, 

 nearly cylindrical, rugose corals; dissepi- 

 mentarium very broad in mature specimens, 

 consisting of large dissepiments elongate 

 parallel to periphery, possibly formed only 

 in late stages ; septa sinuous, dilated ; no 

 axial column ; tabulae numerous, generally 

 incomplete, fine, gently sloping in outer 

 regions, steeply sloping axially, all sloping 

 proximally; septa not reaching axis or per- 

 iphery if dissepiments be present. 



Genotype. — Vesiculophyllum sedaliense 

 (White), 1880. 



Occurrence. — Known only from Chou- 

 teau limestone of Illinois and Missouri. 



Remarks. — This genus dififers from 

 Aphrophyllum Dun and Benson, 1920, with 

 which it is most closely allied, chiefly in 

 having the tabulae, concave upward and in 

 having dissepiments between septa only in 

 very late stage. It resembles Dibunophyllum 

 in having closely packed tabulae at the axial 

 ends of septa, but in the latter genus these 

 are part of a spiderweblike axial structure 

 consisting of tabellae and septal lamellae, 

 whereas in Vesiculophyllum they are tab- 

 ulae only. Septal lamellae and tabellae are 

 not known in Vesiculophyllum, nor have 

 naic septa been observed. 



Aphrophyllum resembles this genus in the 

 relative lengths of long and short major 

 septa. In the obscure cardinal fossula, in the 

 wide similarly formed dissepimentarlum, in 

 the dilated septa, and in lateral compression. 



Vesiculophyllum sedaliense (White) 



Plate 5, figures 5-9; Plate 17, figure 12 



Chonophyllum sedaliense White, 1880, Contr. In- 

 vetrebrate Paleontology, No. 8 p. 157, pi. 39, 

 fig. 3a. Extract from U.S. Geol. Survey, 

 Twelfth Ann. Kept., (1878). 



Chonophyllum sedaliense, Keyes, 1894, Missouri 

 Geol. Survey, vol. 4, p. 116, pi. 14, fig. 9. 



fCyathopJiyllum glabrum, Sardeson, 1902, Am, 



Geol., vol. 30, no. 5, p. 306. 

 ClionopJiyllum sedaliense, Moore, 1927 Am. Assoc 



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

 CJionophyllum sedaliense, Moore, 1928, Missouri 



Bur. Geol. Mines, ser, 2, vol. 21, pp. 128 



154, 195. 



Externals. — Large, slender to thick; epi 

 theca and dissepimentarlum commonly not 

 preserved in mature regions, leaving very 

 irregular surface with edges of septa and 

 tabulae showing; calyx very deep, nearly 

 vertically walled distally; cardinal fossula 

 prominent to obscure ; septa in quadripartite 

 arrangement, pinnate in cardinal quadrants. 



Transverse sections. — In very late ephebic 

 stage (diameters about 32 mm by 35 mm 

 reconstructed), dissepimentarlum occupies 

 half of radius ; dissepiments compressed, very 

 elongate parallel to periphery ; corallite com- 

 pressed ; major septa thick, sinuous; minor 

 septa very short, separated from neighboring 

 majors by concentric dissepiments. 



In middle ephebic stage (diameters 15.2 

 by 18.0 mm incomplete), dissepimentar- 

 lum (when present) occupies ^ of ra- 

 dius; some major septa in part especially 

 thickened, all long; minor septa short; dis- 

 sepiments very sparse between major and 

 minor septa; tabular intersections abundant 

 between septa and in axial region ; corallite 

 compressed in cardinal-counter plane. 



In early ephebic stage (diameters 9.8 by 

 10.3 mm), dissepimentarlum absent; major 

 septa long, thickened ; cardinal and counter 

 septa longest ; tabular intersections abundant 

 between septa, somewhat concentric in axial 

 region. 



In late neanic stage (diameters 6.7 mm by 

 6.9 mm), cardinal septum very long, swol- 

 len at axial end ; counter septum somewhat 

 longer than neighbors, very thick ; septa pin- 

 nate in cardinal and counter quadrants, 

 short; tabular intersections concentric in 

 axial region. 



In very early neanic stage (diameters 2.0 

 by 3.1 mm), cardinal septum a short spine, 

 others not definitely determinable ; tabulae 

 occupy almost all of thecarium ; section 

 quadrilateral with four proto-septa presum- 

 ably occupying corners, as cardinal septum 

 certainly occupies one corner. 



Longitudinal section. — Tabulae rather 

 flat in peripheral area, sloping steeply to- 

 ward apical end In axial area, produced up- 

 ward, obliquely outward short distance 



