ECHINOIDEA. I. 



119 



made 110 note, whether those of Ps. )nacHlata are taken exclusively from the buccal membrane or per- 

 haps also from the test, I do not venture for the present to put too much stress on this feature. The 

 triphyllous pedicellariæ and the spicules show no difference from Ps. indiana. — The features stated 

 here, together with those mentioned by de Loriol and Bell: the size of the peristome and the slits 

 etc., and especially the peculiar coloration, which, according to de Loriol, is not found in iiid/aiia.^ 

 seem to leave no doubt of the faet that they are two well distinguished species. 



In Rev. of Echini» Pseudoboletia like Sphærccliimis is enumerated as a subgenus of Strongy- 

 locriitrotiis^ and at the end of the diagnosis (p. 455) it is thereupon said: «This is an interesting 

 genus, forming, as it were, a link between the Echinometradæ and Echinidæ; its position is still 

 doubtful?. In none of these statements I can agree with Agassiz. Pseudoboletia is neither a sub- 

 genus of Stroiigylocentrotus nor a transitional form between Echinometrids and Echinids, and its posi- 

 tion is not at all doubtful — it is a near relation of Sphærechinus. It agrees with Sphærechinus with 

 regard to the pedicellariæ, the spicules of these, the number of pores, and the structure of the test; 

 only in two features a difference of any importance is found: the spicules of the tube feet are simply 

 bihamate (in Sphærcchimts a little branched in the ends) and — as the more important faet — the 

 buccal piates and the other piates of the buccal membrane are set with small spines and pedicellariæ 

 (in Sphærccliiiiits only with pedicellariæ). That the spines are a little longer and the test somewhat 

 more flattened tlian in Splncrcchinus can hardl\- be used as a generic character. Thus it is rather 

 unimportant characters, by which Psntdoboicfia is distinguished from Sphærccliiniis\ at all events, 

 however, the peculiar covering with spines of the buccal membrane seems to be a sufficient reasou 

 for the keeping of the genu.s, and nothing would be gained by uniting it with Sphærechinus. 



The genus Strongylocentrotus Brandt is in Rev. of Echini (p. 276) enlarged to comprise ..all 

 species having a somewhat circular or subpentagonal, regularly arched or slightly depressed test, with 

 sniooth, imperforate, not crenulate tubercles of uneqnal sizes, forming primary and secondary vertical 

 rows. Pores arranged in arcs of at least four to five pairs. Actinostome decagonal; very slight cuts; 

 buccal membrane bare; spines moderately slender, longitudinally striated, longer proportionally than 

 those of true Echiims^ and more slender than those of Sphærechinusii. According to this diagnosis a 

 great number of species will be referred to this genus, viz. «/fej (Mol.), aniiigcr Ag., dcpressus (Ag.), droba- 

 chiensis (MiilL), crythrograinmus (Va\.), /raiiciscauus (Ag.), Gaimardi (Blainv.), gibhosus (Val.), iiifrn/iedins 

 (Barn.), lividus (Lamk.), »lexicaiius (Ag.), iiudus (Ag.), pnrpurafns (Stimpson), f/ibcrciilafr/s (Lamk.); to 

 which are to be added some species which Agassiz, but no doubt wrongh-, regards a synonyms, viz. 

 chloroccntrotus (Brandt), globulosus Ag. (according to Rathbun, 337. p. 274), and omalostoma (Val.); 

 finally a new species, biillahis, has been described by Bell (46). Further Sphærechimis and Pseudo- 

 boletia are classed as subgenera of Stroiigyloccntrotiis. -The homogenous nature of the genus as now 

 limited cannot fail to be apparent>, says Agassiz (loc. cit). A closer examination shows, however, that 

 this large genus is anything but homogenous. Apart from Sphærechinus and Pseudoboletia there 

 proves to be among the mentioned species at least 6 well characterized genera, which are to be 

 referred to 3 different families! Perhaps still other genera may be represented among the species I 

 have had no occasion to examine. I must grant Agassiz to be right, when he says that it is impos- 

 sible "upon the mere question of quantity or direction of the pores to subdivide this genus >; but for- 



