PERONELLA ORBICULARIS. 521 



The greatest width is anterior to the anterior pair of petals. The petals 

 are narrow. The interporiferous zone is broad ; the poriferous furrows 

 closely packed, diminishing very gradually towards the extremity, where the 

 poriferous zones converge slightly from the apical system towards the ex- 

 tremity, and are not rounded along the sides of the petals. The anterior 

 petal is somewhat larger than the lateral petals. There are four genital 

 openings. The actinal surface is perfectly flat. The actinostome is central, 

 circular, with distinct ambulacral furrows extending nearly to the edge. The 

 interambulacral areas on the lower surface form narrow well-defined bands. 

 The anus is near the edge, elliptical, but placed oblicpiely to the longitudinal 

 axis. The tuberculation of both surfaces is remarkably uniform, but, as in 

 all Laganidae, much larger on the lower surface. The spines correspond to 

 the difference in size of the tuberculation ; those of the upper surface are 

 small, slender, on the lower much larger and stouter ; they are distinctly 

 fluted, with minute serrations along the edge. There are no striking differ- 

 ences to be noted between the larger and smaller specimens. The pillars 

 of the edge of the test are proportionally fully as developed in the young 

 as in older specimens ; the proportions of the petals are not different, though 

 the decagonal outline is not quite as plainly marked. The color of dried 

 specimens is yellowish-brown ; alive they are said to be of a brilliant red 

 color. 



Japan ; New Caledonia ; Bay of Bengal. 



Peronella orbicularis 



Echinodiscus orbicularis Leske, 1778, Kl. Add., p. 144. 

 1 Peronella orbicularis A. Ac, 1872, Rev. Ech., Ft. I. p. 149. 



I have but little doubt that this species will prove to be the young of 

 Peronella decagonalis. Unfortunately all the specimens of P. orbicularis 

 examined are too small to form the connecting link with the youngest 

 specimens of P. decagonalis or of P. rostrata ; there is, however, nothing 

 markedly different which could not be accounted for by a difference of 

 age. The more rounded outline, shorter petals, more swollen edge, 



