13 

 GENUS RECEPTACULITES— De France, (as emended.) 



Generic Characters. — Body consisting of an infundibuliform 

 spreading disc, more or less concave at the centre, depressed- 

 orbicular, and globose. The spreading discoid forms consist of 

 a range of vertical cells in single series ; the orbicular discoid 

 forms have raidiated curving cells which are directed from the 

 center or axis towards the margin, their length and curvature 

 depending on the size and form of the mass ; the foramina or cells 

 in all the forms become larger as they recede from the centre 

 to the periphery, and again become smaller, on the lower 

 side, in the globose forms. Cells cylindrical, contracted 

 below the aperture, and thickened or expanded above, with 

 rhomboidal openings at each extremity. On one side the 

 openings sometimes shows obsolescent rays ; the interior walls 

 of the cells are often striated as if preserving the remains of 

 transverse septa. 



In all these bodies the cells are arranged on curving lines 

 which diverge from the center in a constantly enlarging circle ; 

 these are crossed by similar lines in an opposite direction, 

 which thus leave quadrangular or rhomboidal spaces, " like the 

 engine turned ornament of a watch. "* The form of these 

 apertures depend upon the degree of curvature, or upon the 

 form of the mass to which the curvature of the cell lines will 

 conform. In all cases, however, the cell is cylindrical beneath 

 the exterior. 



Since the cells vary in size at different distances from the 

 center, the size of the cells in separate fragments, affords no 

 means, alone, for specific determination. 



Regarding the form and mode of growth, I have recognized 

 the following species in the Galena limestone of the lead re- 

 gion. 



RECEPTACULITES OWENI— Hall. 



Coscinopora sulcata, (Goldfuss.) Owen, loe. cit., page 40. 



Description. — Body consisting of a broad expanded disc, 

 from four to twelve inches in width, and from one quarter to 

 half an inch in thickness (rarely a little thicker). Surface undu 

 lating with an abrupt fannel shaped depression in the center 

 of the upper side, from which the cell rows radiate in curved 

 lines. 



♦Salter, loc. cit. p. 



