48 S. LOVEN, ON POURTALESIA, A GENUS OF ECHINOIDEA. 



never more nor fewer, as ventral, the sixth of the inner row being intei^mediate, half 

 ventral, half lateral, resembling the preceding in the size and position of its pore and 

 the förra of its simple pedicel, but extending itself inwardly like the succeeding, while 

 the seventh + x following, have their pores transferred towards their opposite, inner 

 extremity, and their pedicels, specialised in a peculiar manner, thus brought within 

 the fasciola. This is the momentous modification of the Spatangean skeleton, brought 

 on for the first time in Micraster during the Middle Cretaceous era. Generally, if not 

 throughout, the subanal pedicels are penicillate, as stated by Johannes Muller, and, 

 at the first glance, they appear to be like those of the phyllodes, only that the disks 

 are somewhat smaller, the filaments more unequal, as if disposed in five groups, and 

 their terminal heads more turaid. On a closer inspection, however, this similarity is 

 found to exist in but very few genera, as far as is hitherto ascertained, only in Echino- 

 cardium, in Lovenia, and perhaps in Breynia. In these the filaments are seen to cover 

 the whole surface of the disk, though not quite so densely as in the phyllodean pedicels. 

 In Echinocardium also the rods are much stronger, more particularly in E. cordatum 

 Penn., Pl. VIII, jig. 57, in which species they are rather thin near the base, and from 

 theuce increase in thickness, so as to become four times as strong as those of the phyl- 

 lodes, spindle-shaped, and nearly solid. The heads of the filaments, among which the 

 marginal ones are the longer, are very tumid. So they are in Lovenia also, the rods 

 being likewise stronger than those of the phyllodean pedicels, Pl. Vill, jig. 59, 60. 

 But, unlike these, the great majority of other genera present a different arrangement. 

 In Spatangus, Maretia, Brissopsis, Kleinia, Brissus, Metalia, and, as it seems probable, 

 in Eupatagus and Linopneustes, among the Prymnodesmians, in Agassizia, Schizaster, 

 Abatus, Hemiaster among the Prymnadetes, the pencil is made up of a few circles 

 only of filaments, placed round the margin of the disk, so as to leave bare its central 

 part, and within this there rises a cupola-shaped or even subglobular protuberance, 

 surrounded by an open circular space, and commonly presenting on its top a central 

 depression, in which about five folds are seen, indicating about five convergent, more 

 or less distinct lobes. In Brissopsis the central protuberance sometimes shows eight 

 to ten such lobes, nearly closing över the middle, sometimes, when subjected to pres- 

 sure, taking the shape of a waved brim all around a flattened cup supported by five 

 calcified areolar lamels, Pl. IX, jig. 85. So it is also in Brissus. In the like manner, 

 the large central protuberance in Kleinia luzonica presents four or five triangulär con- 

 verging lobes almost closing över the middle, while in Spatangus purpureus it is rela- 

 tively small, but high, apparently without any distinct lobes, supported by a convex 

 areolar lamina, and surrounded by a broad circular space, and a marginal crown of 

 filaments with very strong rods and very tumid heads. 



In Agassizia scrobiculata Val., Pl. VIII, jig. 65, the inner filaments are short, 

 and the central protuberance, rising vertically and convex above, presents five tri- 

 angulär, thin, converging lobes, supported beneath by five coarsely areolar, calcified 

 laminEB. In Schizaster japonicus Al. Ag. the whole of the central surface is occupied 

 by the convex protuberance, presenting three to eight subtriangular, convergent, 



