389 



Receptaculites Jonesi. (N. sp.) 



b 



Fig. 365. 



Fig. 365. — Receptaculites Jonesi. a, side view ; b. view of the base. Owing to the 

 peculiar condition of preservation, the grooves of the stolons are imper- 

 fectly seen in this specimen. They are well shown in the fragments of 

 other individuals collected in the same bed with the one here figured. 



Description. — The specimens of this species that have been as yet col- 

 lected are small, turbinate, or depressed conical bodies, from one to two 

 inches across, and from six lines to one inch in height. The broadest ex- 

 tremity, supposed to be the base, is usually circular, sometimes ovate, gently 

 concave, and with an obtusely rounded margin all round, the thickness of 

 which is from three to five hnes. The smaller extremity, or the upper side, 

 is a depressed cone, with an apical angle of 110'=' to 130°, with an irregularly 

 rounded truncated apex. The grooves of the radial stolons, as shoAvn in 

 the cast of the interior of the ectorhin, radiate straight outwards to the 

 margin, and run upwards over tlie rounded edge. There are here (on the 

 peripheral edge) four or five grooves in a width of three lines. The grooves 

 of the cyclical stolons are closer together, there being about nine in the 

 width of three lines. From the margin to the apex both systems of grooves 

 become moi-e crowded together, and, at the apex, the ectorhin appears to 

 have been of a somewhat pliable, coriaceous integument. At the apex there 

 are indications, in all the specimens which have this part preserved, of a 

 small irregularly rounded aperture, which is usually depressed, in form, 

 somewhat like the umbilicus of an apple. 



Several specimens have been collected which show the internal cavity. 

 It varies slightly in form in different individuals, but is, in general, bell- 

 shaped, as represented in fig. 363. (ante, p. 385.) 



None of the specimens yet seen have the ectorhin preserved, and the 

 form of the plates is not, therefore, yet known. Dedicated to (the eminent 

 English naturahst) T. Rupert Jones. 



