NATURAL SCIENCES OF PHILADELPHIA. 85 



these, a double series of minute alternating pieces a short distance along the 

 mesial furrows of each pseudo-ambulacral area, as Dr. White mentions seeing 

 in Granalocrinus Norwoodii* These little pieces do x\oi fill the linear furrows, 

 however, but cover them over, so as to leave a small canal passing along under 

 them, and under the little vault covering the central opening, in such a manner 

 as to communicate through the latter with the visceral cavity within the body. 



From all that is therefore now known, we think there is little room for 

 doubting that at least the little central opening seen in these fossils, in the 

 condition in which the specimens are usually found, is really, in perfect exam- 

 ples, always covered by small pieces in all the different genera. We also re- 

 gard this little covering of minute pieces as corresponding to the ventral disc, 

 or vault, of the typical Crinoids, this part being here reduced, as it were, to its 

 minimum size by the closing in of the surrounding parts. Hence we incline to 

 concur with Dr. White in the opinion that the pieces composing this disc, at least 

 in Nucleocrinus, Granatocri?ms und Pentremi/es stelliforjiiis, if not indeed in all the 

 Blastoids, were not constructed or arranged for being opened and closed at 

 will, to admit food into the mouth, whatever may have been the nature of those 

 covering the other openings. f 



In 1862 M. M. Dujardin and Hupe, who were not aware that any of the 

 openings in the summits of these fossils, excepting the central one in Nucleocri- 

 nus, were ever covered by small pieces, expressed the opinion, in their valuable 

 work on the Echinodermata, that the so-called ovarian apertures in the Blas- 

 toids are not such, but that they and the internal tubesj with which they con- 

 nect, along with the pseudo-ambulacral pores, constitute the respiratory appa- 

 ratus of these animals, while the aperture usually regarded as the anal opening 

 they consider the ovarian orifice. From the fact that they seem to believe that 

 the typical palaeozoic Crinoids were probably nourished by surface absorption, 

 or through the agency of the column, rather than by food taken into a diges- 

 tive apparatus through a mouth, we infer that they suppose the Blastoids had 

 neither anal nor oral aperture. 



In regard to the existence in the palaeozoic Crinoids of a well developed 

 digestive sack, however, analagous to that seen in the existing Criuoids, the 

 discoveries made in this country certainly seem to leave little room for 

 doubts, while it appears to us more in accordance with all that is now 

 known in regard to the general anatomical structure, and the arrangement of 

 the reproductive organs of the living types of the Crinoidea, to suppose that the 

 opening usually regarded as the anus in the Blastoids was really such, or as 

 Dr. White and Mr. Billings maintain, both mouth and vent, than that it was 

 an ovarian aperture. The fact, too, that there certainly seems to have 

 been no direct passage or communication whatever, so far as we have been 

 able to see, between the interior of the internal tubes under the pseudo-ambu- 

 lacra and the general visceral cavity, would also appear to be an objection to 

 the conclusion that they and the external openings with which they connect 

 were really respirator}' organs. 



• These minute pieces we believe extended all the way down the ambulacral furrows 

 in some, if not all types of the Blastoidea, and we even suspect that another series covered 

 the little transverse furrows extending across to the bases of the pinnulse, and possibly 

 up the ambulacral furrows of the latter, as we have seen in the piunute of Balocrinus 

 Christy i. 



t In Pentremites conoicleus, as figured by Dr. Shumard, the small pieces covering the cen- 

 tral opening have, as suggested by him, in their regularity of form and arrangement, 

 much the appearance of the pieces closing the so-called ovarian aperture of the Cydoidea; 

 from which it might be inferred that in this genus these pieces might possibly have been 

 movable, so that they could have opened and closed, as valves. We doubt, however, very 

 much that they could have formed so striking an apparent exception to the corres- 

 ponding parts of other types of the group. We tliink it probable that small openings ex- 

 ist under this little group of plates, at the upper terminations of the ambulacral furrows. 

 This seems the more probable because Dr. S. describes these little pieces as being very 

 differently arranged in Pentremites sulcatus. 



t These are generally more properly folds of a thin calcareous plate, but in the so-called 

 Pentremites stelli/ormis, and other types, each separate fold connects with the inner wall 

 all the way down, excepting at the upper end, so as to form a distinct compressed tube. 



1869.] 



