50 



CHOUTEAU CORALS 



generally absent ; calical floor nearly flat or 

 steeply tilted cardinally. 



Transverse sections. — In late ephebic 

 stage (pi. 12, fig. 2) (diameters 9.0 by 9.3 

 mm), 28 major septa; single septum on 

 either side of counter short, bent sharply 

 toward counter septum; septa of both 

 counter quadrants directed somewhat to- 

 ward counter septum, thicker than septa 

 of cardinal quadrants; septa thick, wavy; 

 two or three tabulae cut centrally. 



Another ephebic section (pi. 12, fig. 1) 

 (diameters 9.7 by 10.0 mm) , with 29 majors 

 extend about J4 of radius; fossula deep; 

 counter septa terminating at edge of a 

 transected tabula; secondary septa (spines) 

 present between primaries, rejuvenescence 

 suggested by outside ring of septal spines; 

 septa of counter quadrants thicker than septa 

 of cardinal quadrants. 



In an earlier ephebic stage (diameter 7.1 

 mm), 27 major septa almost reaching 

 center ; cardinal fossula prominent ; cardinal 

 and counter quadrant septa about equally 

 thickened, all tend to fuse at tips. 



Largest observed specimen (diameters 19 

 by 17 mm), with 36 major septa extending 

 ^ of radius; tabulae nearly flat except 

 where abruptly turned down at cardinal fos- 

 sula. 



Broken calyx of holotype (diameters 9.3 

 by 10.0 mm) with 26 major septa, including 

 recognizable alars ; tips of septa near counter 

 position fused; fusion in other specimens 

 extensive, persisting distally beyond last 

 tabulae. 



Longitudinal-section. — -Tabulae arched up 

 steeply from counter position, then drop 

 sharply from about tips of counter septa into 

 cardinal fossula ; about 4 tabulae in 5 mm. 



Another specimen with 9 or 10 tabulae in 

 10 mm. 



Occurrence. — Localities 1, 2, 8, 9, 48-52» 

 58, 66, ?69, ?76, 84. Keyes' reporting of it 

 from the Burlington is probably erroneous. 



Material. — Specimens studied, 105. Holo- 

 type, University of Cincinnati No. 2238; 

 paratype.s, University of Cincinnati No. 

 2238a; figured cotype of A. blairi Miller, 

 University of Cincinnati No. 3918; other 

 cotype of A. blairi. University of Cincinnati 

 No. 3919; former cotype of Z. chouteauen- 

 sis Miller, University of Cincinnati No. 

 24316; other specimens, some studied. Uni- 

 versity of Missouri Nos. 363, 364, 1043, 



1045, 1132, 1191, not numbered. University 

 of Cincinnati Nos. 24402 (as paratype of 

 Z. tenella), 24403 (as cotype of Z. tan- 

 tilla). 



The specimen here taken as holotype is so 

 listed in the University of Cincinnati col- 

 lection, although Miller did not publish his 

 designation. One of the original paratypes 

 (University of Cincinnati No. 24406) is 

 probably a Cyathaxonia. 



Remarks. — External appearances suggest 

 that several distinct types can be recognized, 

 but the internal structure of the specimens 

 examined by the writer is very stable. Mil- 

 ler's description of A. blairi and A. cornic- 

 ulum are not accurate, and these species 

 were probably differentiated mainly on ex- 

 ternal appearances. The writer believes that 

 the specimen of A. blairi figured by Miller 

 is a cylindrical phase of this variable species. 

 The specimen is incomplete, largely em- 

 bedded in matrix, and badly flaked off, and is 

 certainly not a fitting type. The other types 

 of A. blairi are a much weathered fragment 

 and a piece of coral largely dissolved by 

 acid. 



The writer has selected the specimen 

 figured by Miller (1892, pi. 1, figs. 21, 22) 

 as the holotype of C. corniculum. It is listed 

 as the holotype in the catalogue of the Uni- 

 versity of Cincinnati, but was not oflScially 

 so named by Miller in his work. The types 

 of A. blairi Miller would be the types of the 

 revised species if the writer followed Recom- 

 mendation C of Article 28 of the "Inter- 

 national Rules of Zoological Nomencla- 

 ture," but clarity and stability are better 

 achieved by choosing a specimen of the other 

 species. 



Keyes figured a specimen (1894, pi. 13, 

 fig. 1 ) which is not conspecific with A. blairi 

 Miller because it has much wider spacing of 

 the tabulae. 



C. corniculum may have had an early 

 ephebic stage of long duration, because there 

 are incomplete cylindrical specimens up to 

 15 mm in . length with about 20 septa 

 grouped in three bunches with three thick 

 extensions meeting axially. Other indi- 

 viduals, however, certainly did not have 

 this enduring phase. 



The writer believes that the variable ex- 

 ternal forms recognized In this species relate 

 to variable ecologic conditions. The blairi 

 phase seems most common In impure lime- 



