ECHINOIDEA. I. 



to be used for a quite different series of forms: <iStrongylocentrotusy> tuber culatus etc., which, as will 

 be shown below, do not at all belong to the genus Strongylocentrotus. This would certainly create 

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

 cogent reasons for uniting them. Now such reasons are not found; 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 

 used at all. 



While all the species referred to Tripneustes are no doubt closely allied, the same thing cannot 

 be said of the Toxopneustes-STpzcizs; they form two well distinguished groups. The species pileolus, 

 elegans, and roseus form a group characterized by having only a primary tubercle on every other 

 ambulacral plate, by the peculiar globiferous pedicellariae with a border of spicules and much length- 

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

 variegatus and semitubcr culatus have a primary tubercle on all the ambulacral plates; the globiferous 

 pedicellariae have no border of spicules, the blade is not much lengthened, the bihamate spicules in 

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

 plates 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 semituber culatus with regard to the plates 

 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 pileolus is the type of the genus Toxopneustes' 1 ) 

 of Agassiz, this group must keep this name. The other group gets the name of Psammechinus, 

 which name here gets its definitive place, after having so long been abused (comp. p. 108) ; the numerous 

 names that in the course of time have been applied to Ps. variegatus: Lytechinus, Psilcchinus etc., 

 become only synonyms of Psammechinus. 



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

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

 primary tubercle is only found on every third ambulacral plate; no border of spicules on the globi- 

 ferous pedicellarise , the blade not much lengthened; the bihamate spicules 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 Hipponoe Gray in stead of Tripneustes Ag. Bell (38) maintains 

 that this is unwarranted, as the name of Hipponoe has originally only been published as a nomen 

 nudum, for which no species is given as the type. That Gray himself has later shown Agassiz, 

 which species he regarded as the type of his genus Hipponoe (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 Toxopneustes has first been proposed by L. Agassiz in Observations sur les progres recens de 

 1'histoire naturelle des Echinodermes. (Monographies d'Echinodermes. p. 7.) Dans un travail encore inedit sur les especes 

 vivantes de 1'ancien genre Echinus .... j'ai etabli les coupes suivantes, dont je me bornerai a citer ici les types: Temnopleurus 



(E. toreumalicus) Toxopneustes (E. pileolus)-*. Later, in the preface to Valentin's Anatomic du genre Echinus. p. X. 



Agassiz says of Toxopneustes: Je prends pour type de ce genre f Echinus luterculatus*. As a matter of course pileolns 

 must have the prior right to the name of Toxopneustes. 



