50 SVEN LOVEN, ON POURTALESIA, A GENUS OF ECHINOIDKA. 



vals, answering to the reentering angles between the marginal undulations. Their inner 

 margins and their outer circumference are raised above the rest of the surface. 

 Very similar lamels are seen in Echinoneus, FL Xl,jig. 116, 117, which is homoiopodous. 

 Close under this circlet of areolar lamels there lies, in the last named genus, fig. 117, 

 as well as in Echinoids generally, fig. 114, 115, another set of calcareous ossicles, com- 

 posing what may not improperly be named the foot-ring. This is for the most part 

 composed of a single series of lengthy and arcuated spicules, outwardly smooth, in- 

 wardly areolar and frequently spinose, and placed transvei"sely in such a manner as to 

 overlap one another and to form together a quadrangle, or much more cominonly a 

 ring, encircling the tubular shaft. And, lastly, there follows, through the whole length 

 of the shaft, the series of the well-known min ute, numerous, arcuated and fusiform 

 spicules. 



The pedicels of the Spatangidoe possess calcified tissues answering to those in the 

 Echinidse just describcd. Their phyllodean pedicels, however, seem to be devoid, in 

 the adult, of anything comparable to the strengthening lamellse universally present in 

 the suctorial disks of the Echinida3. It has been shown above that in the phyllodean 

 disk of a very young Echinocardium flavescens, a calcified network is primarily de- 

 posited, evidently corresponding to that seen in the sucking-disk of the young Echinus ^), 

 but also that it gradually dirainishes, being, as it seems, dissolved and converted into 

 the permanent form of the lilamental rods, while the tactual function of the disk is 

 preparing by means of the successive development of additional filaments. And long 

 before these have reached their due number, the primary net-work has disappeared, 

 at least I have searched for it in vain in the adult. It seems to be replaced, very 

 generally, if not universally, by radiating vertical septa, P/. Vill, fig. 64, composed of 

 areolar lamels of irregular form, fig. 78, in some way connected with the annular spi- 

 cules to be described hereafter. And likewise, when the subanal pedicels are constructed 

 upon the model of the phyllodean, as in Echinocardium and Lovenia, there is no trace 

 of strengthening hoi'izontal laminte. 



On the other hand, when the disk of the subanal pedicels is provided with a 

 central protuberance, apparently adapted for sucking, as in the genera enumerated 

 above, this protuberance is often, though, as it seems, not always, underlaid with calci- 

 fied lamin£e, which, however, nowhei^e possess the solidity or the regular form obser- 

 vable in Echinids. Thus in Brissopsis lyrifera, Pl. IX, fig. S5, there are five such 

 separate, but contiguous laminaa, in Agassizia scrobiculata, Pl. VIII, fig. 65, likewise 

 five, of a somewhat triangulär shape, in Brissus compressus IjKmk., fig. 74, five, rainutely 

 areolar, contiguous, outwardly bi- or tri-lobate, while in Brissus raediator n., fig. 75^ 

 and Maretia planulata Lamk., they seem to form a convex, continuous expansion, out- 

 wardly of a more open texture, inwardly closer, supported on the underside by slender 

 radiating ribs. — In the simple slender pedicels, ventral as well as lateral and frontal, 

 the like structure obtains, a terminal combination of about five areolar lamella3 forming 

 a somewhat convex layer, beneath the surface of the top. 



>; Étutles, p. 28, pl. XVII, fig. 149, 150. 



