488 PAL.E0NTOLOGICAL REPORT OF GEOLOGICAL SURVEY. 



mer's description was probably made from some of those furnished by 

 us daring his visit to this country. 



Of the multitudes collected we have now over three hundred speci- 

 mens, and out of this large number, not more than five or six expose 

 the true structure of the body, especially the arrangement of the base, 

 and only two exhibit the pieces at the summit of it. 



OLIVANITES VERNEUILII. Troost. 



(Plate V. fig. 1, la, lb, le, Id.) 



Description. — The body is illipsoidal ; the usual proportion between 

 the height and width is as 4 to 3 ; in the more globose it is sometimes 

 as 3 is to 2^. The whole surface in well preserved specimens, shows 

 a remarkable fine sculpture. The cup, below the ambulacral fields, 

 consists of eleven pieces ; above the cup and between it and the sum- 

 mit are four interradial lanceolate pieces, one anal piece, five pseudam- 

 bulacrse, and ten large pieces ; one on either side of these, making 

 thirty-six prominent pieces, exclusive of those at the summit ; making 

 in all about fifty pieces. Only very short pieces of the column hav- 

 ing been found attached, little of its structure is known ; the small 

 part found attached is round or imperfectly pentagonal. The colum- 

 nar perforation is pentalobate.* 



The Basal pieces, three in number, are very minute; lozenge shaped 

 or quadrilateral; situated at the bottom of the columnar-pit; always 

 concealed when the column is present. 



Primary radials are also three in number; small; situated within 

 the columnar pit; two are hexagonal, and one somewhat lozenge-shaped; 

 nearly of equal size ; each piece is ornamented by three tuburcles, one 

 on either side of the sutures, near the outer margin of the joined 

 pieces, and one near the center of the pieces; they are usually entirely 

 concealed by the column — a single specimen has been seen that ex- 

 hibited a part of these pieces when the column was present. 



Primary radials, second series. These pieces are five in number; 

 forked; one-sixth wider, at the spread of the branches, than high; the 

 inferior margin is deflected within the columnar-pit, and rests on the 

 outer or superior margins of the first radials, as in Pentremites, with 

 this difference, one of the second radials rises from an angular point of 



*A single specimen, out of many, exhibits this structure ; nearly all the specimens are par- 

 tially gilicified, and the structure partially obliterated. 



