538 TRANS. ST. LOUIS ACAD. SCIENCE. 



etching the surface, or by making a cross-section through an am- 

 bulacra! field, and is still more frequently preserved than I first 

 anticipated. Further investigations prove that these canals are 

 only the radiating rays of a pentagonal ring surrounding the cen- 

 tral orifice. In other w^ords, the base portion of the deltoid piece 

 is likew^ise perforated transversely about midways, also the little 

 process on the anterior base portion of the lancet piece, from 

 where this canal runs downwards to the apex of the ambulacral 

 field. This arrangement contradicts the existence of those so- 

 called ovarian pores of Billings* and makes it an impossibility 

 for them to be seen ; for, if they should be seen, it is necessary to 

 cut away a considerable portion of the summit. As these canals 

 are perforating entirely solid calcareous substance and apparently 

 in no direct communication with the hydrospiric sac, I suppose 

 that they served for the reception of the nervous system. 



The " chief novelty," i.e. sublancet plate or subambulacral 

 plate — although confirmed by Mr. Carpenter — I must deny 

 the existence of, and would advise Mr. Carpenter, before 

 making such assertions, to examine the matter more care- 

 fully ; for the truth of the matter is, that there is no such 

 thing as a sublancet plate, and what has been taken for it 

 is only the upper blade of the hydrospiric sac, or the calcare- 

 ous substance from the duct above it (see Fig. i ) ; because imme- 

 diately under the lancet plate lies a duct or vessel (as already 

 FifT. 1. described in my paper), and under this the 



hydrospiric sac. I hardly deem it necessary to 

 give a definition of the difl'erence between the 

 above-named organ and a sublancet plate, which 

 latter could only mean a something like the lan- 

 cet plate, only underlying it. The calcareous 

 substance which is frequently fovmd to fill out 

 Transverse section the duct, or the upper blade of the hydrospiric 



OF A RESTORED AM- , . , . , , , ., ,. 



BULACRAL field:— sac, which is smooth and overlays the plicas, 



a, tentacle ; ^i, hydro- . , , , ,, .,. /• 1 • 1 



spiricsac; r, integu- may mislead to the supposition of having here a 



i^crai*fieiT;°l,^™ rai sublancct plate. The duct has been already de- 

 piece ;«, duct beneath •! J • k. J iu „ „„„„^ z :„ 

 the lancet piece; /, scribed in my paper, p. 7, and the passage 6, in 



pTrfoSgVesame! Wachsmuth's Fig. 4, pt. i., of his Palffiocrinoidca, 

 s, nervous(?) canal. ' .^ j^^tj^j^g ^^^^ t^^^ a fissure between two hy- 



* Palaeozoic Fossils, vol. ii., part i., p. 102, Fig. 63. 



