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



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, PI. XI, Jif/. 116, 117, which is homoiopodous. 

 Close under this circlet of areolar lamels thei'e 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 transversely in such a manner as to 

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

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

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

 spicules. 



The pedicels of the Spatangidie possess calciiied tissues answering to tliose in the 

 Echinidffi just described. Their phyllodean pedicels, however, seem to be devoid, in 

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

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

 disk of a very young Echinocardiuni 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 graduallj' diminishes, being, as it seems, dissolved and converted into 

 the permanent form of the filamental 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, PI. 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 sul)anal pedicels are constructed 

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

 of strengthening horizontal lamina3. 



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 lamina^ which, however, nowjiere possess the solidity or the regular form obser- 

 vable in Echinids. Tluis in Brissopsis Ij^rifera, PL IX, fig. S5, there are five such 

 separate, but contiguous lamina>, in Agassizia scrobiculata, PL VllI, fig. 65, likewise 

 five, of a somewhat triangular shape, in Brissus compressus Lamk., /zy. 74, five, minutely 

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

 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 lamellaj forming 

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



>J Etudes, p. 28, pi. XVII, fig. 149, 150. 



