1879.] NATURAL SCIENCES OF PHILADELPHIA. 233 



the fissures occur not only at the lateral, but also at the upper 

 and lower sides of the plates, meeting here in like manner with 

 the slits of the adjoining plates. In species in which the plates 

 are provided with three slits to a side, the median one is larger 

 than the other two, thus forming with the corresponding slits of 

 the adjoining plate the figure of a quadrangle or rhomb, divided 

 into two triangles, exactly as Billings describes the parallel canals 

 which compose the hydrospires in Caiyocrinus. Indeed, the simi- 

 larity which seems to exist in this respect between the two groups, 

 is so striking, that we can scarcely doubt that both structures 

 were adapted to the performance of the same functions. It is 

 true that the hydrospires in Garyocrinus are located on the aboral, 

 and in the Gyathocrinidse on the oral side of the body, but it must 

 be remembered, as already shown (Am. Journ. Sci., Sept. 1877, p. 

 190) that the entire test of paleozoic Crinoids forms a part of the 

 abactinal system, and the position of the hydrospires in Cysti- 

 deans is by no means confined to the aboral side, nor to the oral 

 in Paleocrinoids. We find in the sen us Porocrinus, Billings, 

 which forms a kind of link between Cystideans and Paleocrinoids 

 (the arrangement of the plates of the calyx is exactly like that of 

 all Cyathocrinidse), that the lrydrospires are altogether confined 

 to the calyx. In the sutures between the plates, there exist a 

 number of striated, poriferous areas, resembling the pectinated 

 rhombs in their structure, and though their form and position are 

 somewhat different from those of any other known Crinoid or 

 Cystidean, there can be no doubt that they performed in the 

 animal the same office. Unfortunately we do not know whether 

 this genus had a poriferous ventral sac ; nor have we been able to 

 ascertain whether the longitudinal depressions on the ventral sac 

 which we have noticed above, were covered perhaps by perforated 

 plates, such as Billings observed upon the tubercles of Garyocri- 

 nus or only the pores and fissures, but we are inclined to think 

 the former was the case, since we found in some other specimens of 

 P. uriicus,r\o depressions, but at the same time no fissures nor pores. 

 In many of the Actinocri?iidse, Platycinidee, and Rhodocrinidse, 

 which are provided with a simple anal tube or an anal opening 

 directly through the vault, the respiratory organs were probably 

 located within the main body, at least there are many facts which 

 seem to indicate this. In an article on page 248 of the Proceed- 

 ings of the Acad. Nat. Sci. Phila., 1878, we noted the existence 

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