88. CONTRIBUTION TO 



PENTRE MITES CONOIDEUS, var. Amplus, n. var. (Rowley), 



Plate 29. Figs. 31, 32, 33-34. 



The width of these specimens is quite as great as the length and the great- 

 est lateral diameter is midway of the body, giving a granatocrinoid form to the 

 fossil. 



There is quite as much difference in form, size and relative proportion of 

 plate length and width between this variety and typical conoideus as there is 

 between/^, godonl Sind P. pi/rifonnls, yet these latter two are regarded as 

 distinct species. Perhaps the intermediate forms in the co7ioideus group more 

 closely unite typical conoideus with variety amplus than variations in the 

 (jodon'i series connect pyrlformis and godon'i. Yet figures in "The Catalogue 

 of the Blastoids in the British Museum," by Etheridge and Carpenter fail to 

 show this fact. 



Accepting, as these authors do, the validity of pyriformis and godoni, 

 they unhesitatingly unite conoideus and koninkanus^ forms as diverse as the 

 former and as easily separated by American collectors. 



Locality and horizen the same as y^ivxetj perlongus, and the types in Mr. 

 G. K. Greene's collection. 



Figure 41 is a specimen of Pentremites conoideus, to show the great 

 thickness of the test just above the base, where the cast of the viceral cavity is 

 exposed to view. At the summit the shell is rather thin. It will also be seen 

 from this figure that the hydrospire folds are imbedded in the thickened test 

 below for nearly half their length, instead of hanging free in the cavity as 

 they do near the summit. 



This is probably a constant character of Pentremites, and is also noticea- 

 ble in some of the granatocrinoids. In Orhitremites noricoodi and Crypto^ 

 hlastus melo, however, the hydrospires are exposed internally, full length. 



Figure 38 is a view of the cavity of a conoideus showing the place at 

 which the hydrospires enter the thickened test. 



Compare this height with the tips of the ambrulacra, either side of the 

 figure. 



Figure 40 is a specimen from which the hydrospires have been removed, 

 exposing the double row of pores piercing the test, beneath each ambulacrum ; 

 also showing the broken ends of the hj^drospire tubes at the summit. 



Figure 37 (x2) is a good view of the hydrospires as seen from the base, the 

 tips being exposed inside the thickened ends of the radials. 



Figure 39 (x2) is a similar drawing, side view, but wdth the ambulacra! 

 tubes broken away in part, the central perforation being exposed at the sum- 

 mit. The anal opening and ventral area are shown as openings through the test. 



