ECHINOIDEA. I. ^c 



spine; it is \ery large and conspicuous in some species, as Ph. hoplacantha.^ Sperosoma Griinaldii a. c, 

 small in Asilirnosoiiia Gnibci, liystrix a. o. These spines are always (?) more or less curved. — In a group 

 of species: Pliormosonia placci/fd, bidsarhii/i, and rigidiivi (a. o.?) the i)riniar\- spines of the actinal side 

 are surrounded by a bag of skin, and their ])oints are swollen in a club-shaped way. In Astlienosonia 

 Grubci^ -jarium., heteractis, and itrois the spines on the abactinal side, primary and secondary ones, are 

 inclosed b\- a thick cutaneous sheath which is constricted one or several times; also in other Echino- 

 thurids, for instance A. liystrix., small bags of skin are seen at the point of the small spines. These 

 spines are distinctly distinguished from the mentioned skin-covered spines in Ph. placenta., btirsanmn, 

 and rjgiduiu b\- being constructed as usual — simple perforated tubes with a long, fine point, while 

 in Pli. placenta etc. they are swollen at the point, and filled by an irregular calcareous net of meshes. 



The tube feet may be arranged in an almost straight line on the actinal side, as in /%. pla- 

 centa., or they may be trigeminous, about as in an Echiinis., as for instance in A.hystrix, or thc\- mav 

 be arranged in three widely separated series, as in Spcrosniiia. In some there is no trace of a suckino- 

 disk on the tube feet of the actinal side, in others there is a well-develoi^ed disk; on the abactinal side 

 a sucking disk is never found. The spicules are almost always rather large, irregular, fenestrated 

 plates situated more or less distincth- in 3 — 4 longitudinal series. In A. varhun., Gritbci, heteractis, 

 and nrcns they are very slightly developed, only small, branched calcareous pieces, rarclv with a hole. 

 — The sphceridite, which follow the tube feet quite up on the abactinal side, show no differences so 

 great that they can be of any systematic importance. The pedicellarise, on the other hand, are of the 

 greatest importance with regard to the classification. 



No less than 5 different kinds of pedicellarite are found in the Echiuothurids, viz. the four 

 kinds known from the Echinids, and further the very beautiful form, described by Wyv. Thomson 

 in ^. feiicstratiiiii^ the tetradacty lous pedicellarias. Only the tridentate and the triphyllous pedicel- 

 larise are found in all Echiuothurids, each of the other kinds are only found in a single genu.s. The 

 tetradactylous pedicellarite have been so excellently described and figured by Wyv. Thomson, that 

 I need not add anything. Globiferous pedicellarite were hitherto unknown in the Echiuothurids; I 

 have found them in A. pellucidiuii (in one of the type specimens from Chall. st. 192; the other speci- 

 mens I have not seen). They are highly primitive; the skeleton consists of three simple rods, a little 

 widened below. No muscles seem to pass between them, which corresponds very well with the fact 

 that the three glandular bags are quite inclosed by a common skin; the pedicellaria cannot be opened 

 as other pedicellaritC. The valves have only half the length of the head, and they are placed between 

 the glandular bags (PL XIII. Fig. 24). There can scarcely be any doubt that this interesting form of 

 pedicellarise is to be interpreted as a very primitive globiferous pedicellaria. 



Neither were ophicephalous pedicellarise hitherto known in the Echiuothurids. The form of 

 pedicellarise figured and described by Wyv. Thomson as ophicephalous pedicellarise, is indisputably 

 the triphyllous pedicellarise, very similar to the triphyllous pedicellarise of the Echinids, only some- 

 what larger. Genuine ophicephalous pedicellarise I have only found in the new form Tromikosoma 

 Koehleri., described here. They are very characteristic, the blade is highly constricted just above the 

 basal part, and abruptly widened above (PI. XIV. Figs. 19, 23, 25). The somewhat contorted arc on the 

 lower side of each valve, so characteristic of the ophicephalous pedicellarise, is here typically developed, 



