242 On the Classijicafory Position of Hemiastcr clongatus. 



Tills Ilcmiastcr lias but two generative pores, " Nur die 

 Genitalporcn der beiden hintern paarigcn Intcrambiilacral- 

 feldor cntwickclt, IMadreporenplatte klein, in der Mitte gele- 

 gcn." The plates represent a tnxe Henu'aster so far as shape, 

 fascicle, peristome, and ambulacra are concerned. The two 

 generative pores arc not upon cones, but they are wide apart, 

 and it is stated in the description of the ])late that the indi- 

 stinct niadreporite has not been rendered by the artist. Its 

 place is evident enough between the posterior costals 1 and 4 

 of Loven. De Loriol remarks that the form belongs to a 

 group of the genus llciniaster in which there are only two, and 

 larelv three, genital pores (instead of four) in the apical disk. 

 He notices that //. cavernosus soinetinies has only two, seldom 

 three pores, and he evidently takes the view that this diminu- 

 tion of the number of generative pores is not to remove the 

 forms from the genus Hcmiaster, all other generic characters 

 being the same. Amongst these characters the presence of a 

 niadrcporic between the posterior ovarial plates does not, in 

 the eyes of this very exact and careful zoologist, militate 

 against the species thus endowed being a Ileinidster. De 

 Loriol's work shows that the number of the pore-bearing 

 plates is a variable quantity, and that too much must not be 

 made of the occurrence in classitication. 



In concluding this reply to the criticisms of Prof. Sven 

 Lovcn, we restore the form which he has removed into the 

 genus P(i/(VOff('nia to its original ]iosition in tlic genus Ilcniias- 

 to'j and its fellow sj^ecies from the higher Tertiary horizon must 

 also be associated wit!i it. The Ranikot and Khirthar Sindian 

 Kummulitie Haniatter elongaius^ Duncan and Sladen, and 

 J-hmiantcr digonus, d'Arch., retain those classificatory terms. 

 "NVe trust that the distinguished naturalist, from whom we 

 liave both learned so much, and for whom we entertain a 

 •sincere admiration, will receive this reply in the same spirit 

 ■which prompted him to notice our work in his great essay on 

 Ponrtalesia. 



Note. — We have used the term " intcrradium " thrcughout 

 this pajicr because it is customary ; but it should certainly be 

 iutenadius. 



September 1884. 



