1885.] NATURAL SCIENCES OF rUILADELPHI A. 263 



plate of the tube forms a part of the calyx. The allied Graphio- 

 crinus, however, has no azygous plate, and the posterior basal, 

 which is somewhat elongate, supports upon its truncate upper 

 end only an anal plate. In Ceriocrinus, which is in a similar 

 condition, the anal plate is partly lifted out from between the 

 radials, and extends half way beyond the articular faces of these 

 plates. In Erisocrinus, the anal plate is not only smaller, but 

 rests wholly upon the radials, beyond the limits of the dorsal 

 cup. Finally in Encrinus, this plate seems to have been entirely 

 removed in the adult. We have a specimen of Encrinus lilii- 

 formis only an inch in length, including the arms, which contains 

 between the arms a row of four conspicuous, slightly convex 

 plates, the upper one triangular, which we regard as plates of 

 an anal tube. This discovery is of some importance, as it tends 

 to prove that Encrinus is not a Neocrinoid, but a highly-developed 

 Poteriocrinoid. 



In the Silurian Triacrinus and Pisocrinus, which we arrange 

 under the Symbathocrinidse, we find dorsally no anal plate, but 

 simply an azygous piece. This supports both posterior radials, 

 which are less than half as large as the two antero-lateral ones, 

 and join laterally. In the Carboniferous genus Symbathocrinus, 

 however, the azygous plate is wanting, the radials are almost 

 equally developed, and these support a small anal piece. In the 

 allied Stortingocrinus and in Stylocrinus (Symbathocrinus of 

 Miller and Schultze), although exclusively Devonian genera, we 

 find neither azygous nor anal plate, but Phimocrinus, like Sym- 

 bathocrinus, possessed a large anal aperture between the highly 

 extended articular facets of the radials, and may have had an 

 anal plate. Whether the summit plates of the two former genera 

 had reached the advanced state of Symbathocrinus, or were } r et 

 in the condition of Haplocrinus, cannot be ascertained from any 

 of the specimens, but it may well be doubted. In Eaplocrinus 

 the anal opening is pierced through one of the interradials, and 

 the same may be the case in Stortingocrinus and Pisocrinus. In 

 Coccocrinus and Gulicocrinus, the anus is located between the 

 first and second radials, piercing the one as much as the other ; 

 in Platycrinus above the first interradial, being separated from 

 the proximals by a special anal plate. 



It has been stated that the Inadunata possess no higher orders 

 of anal pieces, and that the plates succeeding the first, form a 



