q 2 ECHINOIDEA. I. 



Lambert (238. a). 



Fam. Echinometridse. 

 Subfam. Echininse. 



Tribus. Oligoporinse. Triplecliincr^ SchizechincB. 



— Polyporinse. Sphcere china;. Hcliocidaniur, Acrocladince. 



The characters, on which the systems hitherto established have chiefly been based, are: the 

 nnmber of the pores, the breadth of the ambnlacral areas, the slits and form of the test. Desor 2 ) is 

 the first author, who nses the number of the pores as a principle of division, dividing the forms 

 belonging here into «01igopori» and <Polypori>. In this he is followed by all the later authors (even 

 if they do not use the expressions of 01igopori» and Polypori*) with the exception of Pom el and 

 Bell. In the essay on the Echinometrids quoted above, Bell has given a thorough criticism of this 

 feature, and has shown that it is by no means a natural principle of division, in spite of the assertion 

 of Agassiz (Rev. of Ech. p. 423) that 'this division, although it appears a numerical one, is yet one 

 of great physiological importance, as the mode of growth of the poriferous zone in these two families 

 is totally unlike . I must assert, still more strongly than has been done by Bell, that this division 

 is a quite numerical one, not at all corresponding to the natural relation of the forms. Moreover it 

 cannot be carried through at all, some species having on the lower ambulacra! plates (i.e. as young 

 individuals) trigeminate pores, on the others multigeminate ones. Besides the instances mentioned by- 

 Bel 1: Echinostrcphus, Strongylocentr. drobachicnsis, Echinometra macrostoma and other Echinometra- 

 species, I can name «.Strongyloccntrofits alius and lividus that have also only three pairs of pores in 

 the lower ambnlacral plates. Also in young Spha-rechinus granularis trigeminate pores may be found 

 in the lower plates, and this feature, I think, may be taken to be found in all polypore forms. When 

 Bell, in his group of Echinince, uses the number of the pores as a base of further subdivision, I can- 

 not agree with him; so much importance is not due to this feature, it can by no means be regarded 

 as more than a generic character, and I should not wonder, if in some cases it should prove to be no 

 more than a specific character. At all events the number of the pores has only slight importance 

 or none at all with regard to the natural grouping of the genera; Pom el seems to be the only author, 

 who has hitherto seen this fact. 



The breadth of the ambnlacral areas is used by Gray as a distinguishing character. That it 

 is especially unfortunate is shown by the result, as Gray thereby is brought to the uniting oiAmbly- 

 pncustes, Holopneztstes, Boletia, and Hipponoe into one family, what is absolutely wrong; neither has 

 any author followed him in this respect. 



The slits of the test are used by Pomel and Troschel, by the latter, however, only as a sub- 

 ordinate character, the number of the pores being used as the first principle of division, so that only 

 the forms with trigeminate pores are referred to his family Tripnctistida , while Sphar echinus and 

 Pscudobolctia are referred to the family Toxopneustida. — Agassiz says of the deep slits of the test 

 in Spharechinus (Rev. of Ech. p. 451): «the presence of deep, sharp cuts in the actinal system ... are 

 simply quantitative characters, the value of which a better acquaintance with the subject will deter- 



') Synopsis des Echinides fossiles. 1855. 



