48 



CHOUTEAU CORALS 



In late ncanic stage (diameters 5.5 by 

 4.7 mm), 19 major septa, counter, cardinal, 

 and two others in cardinal quadrants meet 

 at tabular intersection near axis of coral. 



Longitudinal section. — Not ground be- 

 cause of rcmarkabl)^ deep calyx. 



Comparison. — This species can be dis- 

 tinguished by the extraordinarily thick 

 epitheca, very deep calyx, lack of strong 

 inclination of calyx, and by the tendency 

 toward distal flaring of corallite. 



Occurrence. — Localities 1, 2, 7. 



Material. — Specimens studied, 9. Holo- 

 type and paratypes, University of Missouri 

 not numbered ; ideotypes, University of Cin- 

 cinnati Nos. 24309, 24319 and University 

 of Missouri No. 1052 and not numbered. 



Appendix to the Hapsiphyllidae 

 Genus and species unidentified 



Plate 17, figures 13. 14 



Description. — Curved, trochoid, simple; 

 epitheca spinose, flattened on convex side; 

 calyx deep, with 38 major septa, cardinal 

 fossula on convex side; dissepiments in three 

 or four rows, concentric. 



Early ephebic stage, at diameter of about 

 7 mm, short cardinal septum flanked on one 

 side by 8 thick major septa and one other 

 side by 7 thick septa ; axial ends of each 

 group fused ; counter septum long, thin, 

 flanked on either side by 5 shorter thin major 

 septa with ends axially free ; tabulae arched 

 rather sharply distally. 



Occurrence. — Locality L 



Material. — Specimen studied, 1. Univer- 

 sity of Chicago No. 31591. 



Remarks. — This specimen has the shape, 

 spines, tabulae, dissepiments, and apparent 

 septal arrangement of Allotropiophyllum 

 Grabau, 1928, but in that genus the septa 

 of the counter quadrants from a continuous 

 inner wall and the septa of the cardinal 

 quadrants are free. Thus, the primary sym- 

 metry is reversed. There can be no doubt 

 that this specimen is the reverse of Allotrop- 

 iophyllum because study of interseptal ridges 

 bears out the orientation as seen in sections. 

 Allotropiophyllum as interpreted by Hill 

 (1940) differs from the diagnosis given by 

 Grabau in that there are no dissepiments. 

 Under the circumstances it is not advisable 

 to assign this specimen to any existing genus, 



and a new group should not be erected to 

 contain it until further material is available. 



Genus Amplexus Sowerby, 1814 



"Simple cylindrical Rugose corals with thin, 

 short septa which are fully developed only on the 

 upper surfaces of the tabulae, but above these 

 extend progressively a shorter distance from the 

 epitheca. The tabulae are widely spaced, flat and 

 complete, and there are no dissepiments." (Hill, 

 1940, p. 147.) 



Genotype. — Amplexus coralloides Sower- 

 by, 1814. 



Occurrence. — Supposedly from Silurian 

 to Permian in many parts of the world. 



Remarks.— mW (1940, pp. 147, 148) 

 regards Amplexus of authors as a poly- 

 phyletic group. Amplexus rockfordensis 

 Miller and Gurley has thickened septa in 

 the cardinal quadrants in as late as the 

 ephebic stages, and thus dilTfers from the 

 genotype which has thin septa. Ordinarily, 

 such a pronounced difference would be con- 

 sidered ample basis for generic separation, 

 but until species of Amplexus can be re- 

 viewed a new genus should not be erected 

 for this one species. 



Amplexus rockfordensis Miller and 

 Gurley 



Plate 12, figures 4-8; Plate 17, figure 15 



Zaphrentis Ida Winchell, 1865, [in part], Phila- 

 delphia Acad. Nat. Sci., Proc, p. 111. 



Amplexus ( ?) rockfordensis Miller and Gurley, 

 1897, Illinois State Mus. Nat. History Bull. 

 12, p. 53, pi. 3, figs. 22, 23. 



Amplexus? rockfordensis, 1899, Kindle, Bull. Am. 

 Paleontology, vol. 3, bull. 12, p. 162. 



Externals. — Large, curved ceratoid to 

 nearly cylindrical ; epitheca thin with broad 

 spines hollow at their bases and of unknown 

 length, striae, rugae, interseptal ridges; 

 axial increase, geniculation observed ; one 

 specimen 28 mm in maximum diameter, 90 

 mm along convex side (incomplete) ; an- 

 other specimen with small shallow cardinal 

 fossula. 



Transverse sections. — At diameter of 24 

 mm (very late ephebic stage of a cylindrical 

 specimen), 29 major septa extending 1/4 of 

 radius; minor septa existing as spines, 

 largely restricted to counter quadrants; 

 counter septum half again as long as other 

 majors. 



At diameter of 22 mm in ceratoid speci- 

 men (late ephebic stage), 36 major septa, 



