ECHINOIDEA. I. ., 



found OU the large pedicellariæ; when this is the case, tlie spi- 



ciiles (fenestrated piates) will show that it is no Doroddaris) 3. 



The large globiferous pedicellariæ with large moiith; the blade not 

 prolonged. The stalk has 110 limb of projecting calcareous ridges. 

 The small pedicellariæ withont end-tooth. The spiciiles fenestrated 



piates Stercocidaris ingolfiana Mrtsn. 



The large globiferous pedicellariæ with a little niouth at the 

 end of the somewhat prolonged blade. The stalk with a limb of 

 projecting calcareous ridges. The small globiferous pedicellariæ 

 with end-tooth. The spicules .spinous arcs Cidaris afjinis Phil. 



Fam. Echinothuridæ. 



The classification of the Echinothurids is distinguished by a pleasing simplicity; only three 

 recent genera are knowu, P/ioriiiosoiiia, ^[stJiaiosonia and Spcrosoiiia ^ and, what is still more pleasing, 

 there are only two synonyms of these names, viz. Calvcria W. Th., and Cyaiiosoiiia Sarasin. To the 

 genus Phormosovia 10 species have been referred, to Asihaiosovia 11, and to Sperosotna 2 species, most 

 of which species have been described by A. Agassiz, the rest by Wyv. Thomson, Koehler, Doder- 

 lein, and Yoshiwara, all during the last three decades. Here, then, we .seem to have a division of 

 Echinids where the classification is in the best possible order. — The joy, unfortunately! does not last 

 longer than until the moment when one has to determine Echinothurids oneself. Then one will soon 

 reecho the complaint of S ara. sin: Wir wis.sen niclit, waruni es A. Agassiz seinen Lesern .so sehr 

 saner gemacht hat sich in seinen Challenger Echiniden zurecht zu finden. Um einen Ecliiuothuriden 

 daraus zu bestimmen ist es notig die bei den einzelnen Arten gemachten Angaben sorgfåltig zu ana- 

 lysieren, initer Rubriken zu ordnen und dann die Bestinunung zu versuchen (352. p. 96). We niight, 

 however, let that pass, if all the difficulties were to be superseded in this way; but this, unfortunately, 

 is not the case, as it will soon appear that the two large genera, P/ioniiosoiiia and Astliciiosoina^ are 

 in reality not to be distinguished from each other with certainty. 



The chief difference between these genera is stated to be the faet that in Phoriiiusoiiia the 

 piates overlap each other in the whole length of the edge, while in Asthcnosoiiia the piates are 

 narrower in the middle, so that naked interspaces are left only covered by the skin; only the broader 

 ends of the piates overlap each other in the way peculiar for the Echinothurids. Now there i.s, 

 however, the drawback by this statement that the arrangement of the piates is generally only to be 

 seen in dried specimens. But the Echinothurids are only very little adapted for preservation in dried 

 State, and if the material in hånd be slight, one does not like to destroy it for the sake of determina- 

 tion. And even if the material is copious enough, so that it is possible to examine the piates exactly, 

 we are by no means sure to arrive at a result. Bell (72) has shown that there is a considerable varia- 

 tion as to the size of the uncalcified membranous space between the piates: this may be quite couspi- 

 cuous or calcification may have gone so far, that it is difficult to detect the membranous interspace. — 



