332 Messrs. Duncan and Sladen's Objections to the 



no. 7, 1883), regarding the variations in the apical system of 

 Ecliinoidea, so we give a few extracts which may be readily 

 verified. 



The delineations are wonderfully correct and artistic in 

 Lov^n's ' Pourtalesia,' 1883, pi. xviii. Take first of all a 

 specimen of Spatangus purpureus as large as many fossil 

 Hemmsters, 16 : 15 millim., it has no genital pores ; a slightly 

 smaller one, 15 : 14 millim., has two genital pores and a 

 madreporite ; a specimen 24 : 21 millim. has only two genital 

 pores ; and one slightly smaller has one pore only and the 

 madreporite has openings in the posterior basal (genital) plates 

 besides along its course which separates the basals and poste- 

 rior ocular (radial) plates. A specimen 23 : 22 millim. has 

 four genital pores and the madreporite even extends into the 

 posterior interradium. In Bn'ssopsis lyrifera (Loven, pi. xix.) 

 a specimen 15 : 12 has two genital pores, but both are in the 

 plates of the left side ; a specimen 15 : 13 millim. has but one 

 genital pore and that in the left posterior basal ; a specimen 

 16 : 13 millim. has four genital pores, and one 42 : 28 mil- 

 lim. has only three genital openings, and there are isolated 

 madreporic pores in the posterior interradium. 



One of our species, H. decipiens, which we described in 

 1883 in the Ecb. from Kach and Kattywar, Pal. Ind. ser. xiv. 

 p. 34 (we give the reference because it was omitted by M. 

 Cotteau), is now determined by M. Cotteau to be a Trachy- 

 aster, although he admits that the apical system is not visible ! 

 It so closely resembles Lmthia in shape that we called it 

 " dect2nens'^^ but there is no lateral fascicle. The Trachy- 

 asterian characters are absolutely absent. We must confess 

 that all this lax taxonomy does not appear scientific ; but 

 before leaving this part of the subject it is necessary to exa- 

 mine Mecaster, Pomel {op. cit. p. 42). 



This genus is placed by M. Pomel immediately before 

 Hemiaster, Desor, and in a different subfamily from Tracliy aster ^ 

 the sole difference between these so-called genera being that 

 in Mecaster the madreporite separates the posterior ocular 

 plates as well as the posterior genital plates ! 



It appears from M. Cotteau's article in the Pal. Fran9. 

 Ech. 1887, that he was aware of M. Gauthier's excellent 

 article upon the impropriety of forming genera upon the posi- 

 tion of the madreporite (Assoc. Fran^. 1886, published 1887, 

 p. 406) before altering the Hemiasters into TracJiy asters. 

 M. Gauthier's reasoning is incontrovertible as regards the 

 genus Hemiaster^ and he showed and delineated specimens of 

 the same species in which the position of the madreporite was 

 exceedingly variable. Yet this cogent reasoning is passed by. 



