HYDROZOIDS AND CORALS. 105 



Horizon and locality. — Devonian, Hamilton limestone : St. 

 Louis county. 



The American corals of this group appear properly to be- 

 long under Oyathophyllum, as has already been announced by 

 Rominger. The internal wall, which is said to be so character- 

 istic of Acervularia, is rarely, if ever, well defined, in the forms 

 under consideration. The nearest approach to the annular 

 wall appears to be the enlargement of some of the smaller 

 lamellae along the inner margins. But in no case have these 

 thickenings been observed, in connection with the alternating 

 larger septse, to form a closed ring. 



In those specimens in which the growth of some of the 

 corallites has been accelerated more than others, the calyces 

 have assumed a circular instead of polygonal shape as in 

 CyathopJiyllum ccespitosum Goldfuss, and other more typical 

 forms of the genus. 



Cyathophyllum cornicula Kominger. 



Plate xli, fig. 4. 

 Cyathophyllum cornicula Rominger, 1876: Geol. Sur. Michigan, vol III, pt. 

 ii, p. 102, pi. XXXV, fig. 2. 



Very similar to G. glahrum, which, however, differs from 

 this form in being more slender, in possessing a very deep 

 calyx, in the greater number of lamellae, and in having the 

 surface smooth, instead of conspicuously annulated. 



Horizon and localities. — Devonian, Calaway limestone : 

 Winfleld (Lincoln county). 



At present, data are not at hand to satisfactorily deter- 

 mine whether or not this form is identical with CaryopJiellia 

 cornicula of Lesueur, or Zaphrentis cornicula of Milne-Ed- 

 wards. 



Cyathophyllum glabrum s^. now. 



Plate xli, figs. 6a- b. 



Corallum simple, turbinate, moderately curved, annulated 

 by broad folds; base attenuated. Calyx very deep, lamellae 

 numerous, 80 to 100 in number ; interlamellar spaces occupied 

 by transverse plates, but leaving the inner margin of the ver- 

 tical septae free, and making the peripheral area quite vesiculose. 

 G— 8 



