KCIIINOIDEA. I. II9 



made no note, whether those of Ps. maculata 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 pedicellarise 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 Indiana, 

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



In Rev. of Echini > Pseudoboletia like Sphatrechinus is enumerated as a subgenus of Strongy- 

 locentrotus^ 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 Echinometradae and Echinidse; its position is still 

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

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

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

 regard to the pedicellarise, 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 Sphcerechinus a little branched in the ends) and --as the more important fact — the 

 buccal plates and the other plates of the buccal membrane are set with small spines and pedicellariae 

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

 more flattened than in Sphccrcchiniis can hardly be used as a generic character. Thus it is rather 

 unimportant characters, by which Pseudoboletia is distinguished from Sphcerechinus; at all events, 

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

 for the keeping of the genus, and nothing would be gained by uniting it with Sphcerechinus. 



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 

 smooth, imperforate, not crenulate tubercles of unequal 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 Echinus, and more slender than those of Sphcerechinus*. According to this diagnosis a 

 great number of species will be referred to this genus, viz. albus (Mol.), armigerAg., depressus (Ag.), droba- 

 chiensis (Mull.), crythrogrammas (Val.), franciscanus (Ag.), Gaimardi (Blainv.), gibbosus (Val.), intermedins 

 (Barn.i, tividus (Lamk.), mexicauus (Ag.), nudus (Ag.), purpuratus (Stimpson), tuberculatus (Lamk.); to 

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

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

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

 boletia are classed as subgenera of Strongylocentrotus. 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 Sphcerechinus 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- 



