74 PALAEONTOLOGY OF ILLINOIS. 



ZAPHRENTIS PELLAENSIS. (sp. uov.) 



PI. IX, Figs. 6-Ga and PI. X, Fig. 11-lla. 



Corallum turbinate, regularly curved, height of an average 

 specimen 1% in., diameter of calyx about % in., depth of cup % 

 in.; sides descending abruptly, the lamellae on each side of the 

 fossette to the number of four to six coalescing, while the others 

 extend singly nearly to the center of the cup. Fossette narrow 

 and situated obliquely to the curvature of the corallum. Whole 

 number of the principal lamelke 32 to 36 with about the same 

 number in the secondary series. Surf ace moderately rugose and 

 often marked by a few short scattering spines that are usually 

 restricted to the lower portion of the corallum. 



This form is closely related to Z. spinulosa, E. & H. from the 

 Chester beds, but is usually shorter in proportion to its dia- 

 meter, and coming from a different geological horizon it is entitled 

 to be considered as a distinct variety. 



Position and locality: St. Louis shales, near Pella, Iowa. 



Collector, A. H. Worthen. 



No. 2605 of the Illinois State Museum. 



ZAPHRENTIS CALCARIFORMIS. Hall. 



PI. X, Figs. 2-2a. 



This form was described in the Thirty-fifth Annual Report of 

 the New York State Museum of Natural History, page 33, as a 

 Devonian species, from the Falls of the Ohio. The following is 

 the original description. 



"Corallum simple, narrowly turbinate, regularly curved; dia- 

 meter of calices in individuals of the same height varying from 

 ten to fifteen millimeters; height twenty-five millimeters: ex- 

 terior with frequent undulations and low rounded annulations: 

 fossette narrow, very deep, commencing at the center and con- 

 tinuing to the posterior margin ; the lamellae extend to the 

 margin; coalescing and forming vertical walls; number of 

 lamellae fifty, alternating in size; at a distance of two milli- 

 meters from the margin the smaller lamellae coalesce with the 

 others." 



The specimen figured is an unusually long one, but presents 

 the usual characters of the species. 



