114 



ECHINOIDEA. I. 



to be iised for a quite different series of forms: :Stroiigyloccntrotus> tiibercjilatus etc. , which, as will 

 be sliown below, do not at all belong to the genus Strongyloccii trohis. This woiild certainly create 

 mucli confusion, and only to avoid this calamity these genera ought to be kept np, if there are no 

 cogent reasons for iiniting them. Now such reasous are not fonnd; on the contrary a closer examina- 

 tion shows that other characters are found, more reliable than those given by Agassiz, which char- 

 acters may also be used for the small specimens, where the characters mentioned above cannot be 

 iised at all. 



While all the species referred to Tn'pneustcs are no doubt closely allied, the same thing cannot 

 be said of the Toxop)iciistcs-?,-^^c\^s,\ they form two well distinguished gronps. The species pilrohis^ 

 elegans^ and rosens form a group characterized by having only a primary tubercle on every other 

 ambulacral plate, b}- the pecnliar globiferons pedicellariæ with a border of spicnles and mnch length- 

 ened blade and end-tooth, and by the branched bihamate spicnles in the tnbe feet. The species 

 variegatus and semititbercnlatns have a primary tnbercle on all the ambulacral piates; the globiferons 

 pedicellariæ have no border of spicnles, the blade is not mucli lengthened, the bihamate spicnles in 

 the tnbe feet are not branched in the ends. That the buccal membrane is more richly provided with 

 piates and the spines longer than in the former group, I take to be less reliable characters, especially 

 as there is a rather great difference between variegatus and semituberculatus with regard to the piates 

 of the buccal membrane. Thus the two groups are seen to be very well distinguished, and each of 

 them ought no doubt to form a separate genus. As pileohis is the type of the genus Toxopnei/sfes^) 

 of Agassiz, this group must keep this name. The other group gets the name of Psaiin/iecl/inus., 

 which name here gets its definitive place, after having so long been abused (comp. p. io8) ; the numerous 

 names that in the course of time have been applied to Ps. variegatus: Lytecliiuus^ Psilecliiiiiis etc, 

 become only s)-nonyms of Psauivicchimis. 



After having thus limited the genus Toxopnenstcs, it is easy to state the characters, by which 

 the genus Tripneustes is distinguished as well from the former genus as from PsaDuiiecliiniis. A 

 primår}' tubercle is only found on every third ambulacral plate; no border of spicnles on the globi- 

 ferons pedicellariæ, the blade not mnch lengthened; the bihamate spicnles in the tube feet not 

 branched in the ends. To these characters is then to be added with regard to the larger specimens 

 the characteristic arrangement of the pores in three separated longitudinal series. — In Rev. ofEch.» 

 Agassiz has adopted the name of Hippouoe Gray in stead of Tripiieiistes Ag. Bell (38) maintains 

 that this is unwarranted, as the name of Hippouoe has originally only been j^ublished as a nomen 

 nudum, for which no species is given as the t}'pe. That Gray himself has later .shown Agassiz, 

 which species he regarded as the type of his genus Hippouoe' (Agassiz, 7), does not justify the adop- 

 tion of this name, any more than the assertion of Agassiz senior that if the name of Hipponoe proves 

 to be a synonym of his Tripneustes^ the former is to be preferred (Introd. to Valentin's Anat. du 

 genre Echinus. p. IX.). As well known the author of a name has himself no more command of it 



') The name of To.xopneustes has first been proposed b}- L,. Agassiz in . Obsen-ations sur les progrés récens de 

 l'histoire naturelle des Echinodermes;>. (Monographies d'Echinodermes. p. 7.) «Daus un travail encore inédit sur les espéces 

 vivantes de l'ancien genre Echinus . . . . j'ai établi les coupes suivantes, dont je me bornerai å citer ici les types: Temnopleuriis 

 \E. toreztmaiictis), .... To.xopneustes {B. pi!eolus)a. Later, in the preface to Valentin's < Anatomie du genre Echinus». p. X. 

 Agassiz says of Toxopneustcs: «Je prends pour type de ce genre f Echinus luierc7c/atus». — As a matter of course pileolus 

 must have the prior right to the name of Toxopnenstes. 



