SPONGES, GEAPTOLITES, CORALS. 57 



Keceptaculltes owenl.l 



diameter of this species is from four to twelve inches, and nearly every specimen 

 obtained preserves the nucleus. Fragments are rare, but when secured prove 

 to be portions not far removed from the nucleus. If R. oweni were originally a 

 spherical or pyriform body, we should expect to find fragments of the upper 

 portion, and these could be readily determined by the impression left by the 

 head-plates. Such parts have not been discovered in the Northwest. Further, 

 it is stated that "the genus Ischadites agrees essentially with Receptaculites in 

 structure, but its skeletal elements are more slender." We fail to find an in- 

 ternal integument in Ischadites, or the lateral extension of the vertical rays in the 

 "gastral" cavity; they have been observed as terminating freely, and pointed at 

 their extremities, in specimens of Ischadites iowensis, but apparently end bluntly in 

 Lepidolites. It may be that the lateral extension of the vertical rays of the spicules 

 forming the upper integument in R. occidentalis and R. oweni served the same purpose 

 as the large number of plates discovered by Herr Banff', closing the heretofore sup- 

 posed apical opening in Ischadites, i. e. for the regulation of the water currents. These 

 lateral extensions of the vertical rays of the upper surface in R. oweni are traversed 

 by from ten to twelve horizontal canals. 



RECEPTACULITES OWENI Hall. 



PLATE F. FIGS. 1-4. 



1844. Coscinopora sulcata OwEN(non Goldfuss). Geological Report of Iowa, Wisconsin, and Illinois, 



p. 40, pi. 7, flg. 5. 



1861. Beceptaculites oweni HALL. Report of the Superintendent of the Geological Survey of Wiscon- 



sin, p. 13. 



1862. Receptaculites oweni HALL. Geological Report of Wisconsin, p. 46, flg. 2, and p. 429. 



1868. Receptaculites oweni MEEK and WORTHEN. Geological Survey of Illinois, vol. iii, p.302, pi. 2, flg. 3. 



1882. ReceptacMlites oweni WHITFIELD. Geology of Wisconsin, vol. iv, p. 239, pi. 10, flg. 7. 



1883. Receptaculites oweni HALL. Twelfth Rep. State Geologist of Indiana, p. 243, pi. 1, flg. 1. 



1884. Beceptaculites owitjentalis (partim) HINDE. Quart. Jour. Geol. Soc. London, vol. xl, p. 842. 



Original description. "Body consisting of a broad expanded disc, from four to 

 twelve inches [even twenty inches] in width, and from one quarter to half an inch 

 | sometimes 20 mm.] in thickness (rarely a little thicker). Surface undulating with an 

 abrupt funnel-shaped depression in the center of the upper side [with a small conical 

 projection on the under side], from which the cell rows [head-plates of the spicules | 

 radiate in curved lines. 



" The thickness in the center is not more than one-eighth of an inch, and at a 

 distance of three or four inches from the center is less than half an inch : cells [ver- 

 tical i-ays of the spicules] cylindrical in the middle and contracted both above and 

 below [from 1 to 3 mm. in diameter], the walls of the cavities often showing trans- 

 verse striae, which appear like the remains of septa [since these cavities are casts of 



