34 



CHOUTEAU CORALS 



3502; other specimen, University of Cint 

 cinnati No. 24401 (as paratype of Z. 

 tenella). 



Remarks. — The types were formerly part 

 of the cotypes of Z. calycula Miller. 



Family Streptelasmidae Grabau, 1922 



PsEUDOCRYPTOPHYLLUM Easton n. gen. 



Diagriosis. — Simple, rugose corals; six 

 primary septa in earliest stage observed, 

 three (cardinal and alars) persistently 

 strongest, longest; counter septum very 

 strong in early stage, rapidly becoming 

 weak, persisting into most advanced stage 

 observed; minor septa, if any, confined to 

 counter quadrants, well developed only in 

 early stages ; tabulae present, thick near cen- 

 ter, very thin periaxially; dissepiments ab- 

 sent. 



Genotype. — P seudocryptophyllum cavum 

 Easton n. sp. 



Occurrence. — Chouteau limestone (unre- 

 stricted), Pettis County, Missouri. 



Remarks. — This genus differs from Cryp- 

 tophyllum in having six early septa, counter 

 septum strongly developed early in onto- 

 geny and persisting into late stages, sec- 

 ondary septa almost restricted to early 

 stages. It differs similarly from Plerophyl- 

 lum but also the orientation of Plerophyl- 

 lum is the reverse of that in Cryptophyllum 

 and Pseudocryptophyllum. Plerophyllum 

 may prove to be synonymous with Crypto- 

 phyllum, but the Chouteau species must be 

 placed in another genus on the basis of the 

 six early septa and the strong counter sep- 

 tum in early stages. Both Plerophyllum and 

 Pseudocryptophyllum have walls of epitheca 

 fused with the extreme outer portions of 

 septa. The tabulae of Cryptophyllum and 

 Pseudocryptophyllum are similar in being 

 axially depressed. Pseudocryptophyllum may 

 have been derived from Cryptophyllum by 

 additional reduction in the length of sec- 

 ondary septa and reduction in the strength 

 (not necessarily length) of the counter sep- 

 tum. This is not borne out by the strati- 

 graphic occurrence of the species, however, 

 for the monotypic Cryptophyllum extends 

 from Zg into Dg of the British section — 

 a range which includes almost the entire 

 Lower Mississippian of America. 



Pseudocryptophyllum cavum 

 Easton n. sp. 



Plate 4, figures 8-11 ; Plate 16, figure 31 



Externals. — Small, straight, ceratoid ; epi- 

 theca thin with definite interseptal ridges 

 and septal grooves, spines very sparse; cor- 

 allite expands increasingly rapidly. Calyx 

 not observed. 



Transverse sections. — In late ephebic 

 stage (9.3 by 8.3 mm) three very prom- 

 inent dilated septa, cardinal and alars; 

 counter short, flanked by axially somewhat 

 swollen longer counter-lateral septa on either 

 side ; fairly well-defined traces of secondary 

 septa irregular in counter quadrants, else- 

 where secondary septa only swellings on 

 periphery; all majors connected by strongly 

 developed transected tabulae near axis; 

 outer tabulae very thin. 



In late neanic stage (diameters 4.3 by 3.5 

 mm), six prominent septa meeting at solid 

 axial structure which is in reality a thick 

 tabula; counter septum much the most di- 

 lated but shortest; rather well developed 

 septal traces of secondaries in counter 

 quadrants join transected tabula in slightly 

 earlier stages ; tabulae thin. 



At very slightly more advanced (early 

 ephebic) stage, septa extend almost to cen- 

 ter, fail to meet at tabular intersection; 

 counter much weakened, it and counter-lat- 

 erals shortest of six septa present. 



Longitudinal section. — Tabulae arch 

 steeply upwards with slight axial sag; may 

 be recurved upwards at peripheries; vari- 

 able in thickness. 



Comparison. — The six long major septa 

 serve at present to differentiate the species. 



Occurrence. — Localities 8, 38. 



7l^«/^r/^/.— Specimens studied, 2. Holo- 

 type. University of Missouri not numbered ; 

 a possible representative is Illinois State 

 Geological Survey No. 3510. 



Remarks. — The orientation of the speci- 

 men was obtained from a study of the inter- 

 septal ridges and septal grooves. 



Family Hapsiphyllidae Grabau, 1928, 

 emend. Easton 



Diagnosis. — Simple rugose corals whose 

 major septa tend to surround a prominent 

 cardinal fossula; minor septa may be pres- 



