Hamhach — Revision of the Blastoideae. 9 



1-3, because Pentremites schultzii and paillettei are as typi- 

 cal Pentremites as sulcatum, pyriformis and others, — that is 

 to say, their calyx consists of the same number of pieces with 

 the same relationship of them to each other as in the true 

 Pentremites. Their genital openings are constructed by the 

 junction of deltoid and lancet pieces precisely as we find 

 in the typical species above mentioned. Other differences in 

 the character of this genus as lately revised are of no generic 

 value as they are due to the variability in size and shape of 

 basal, fork and lancet pieces, and are only of specific impor- 

 tance. 



That the general conception of the deltoid pieces is not a 

 correct one is sufficiently shown by the descriptions given by 

 various authors. They were called interscapular plates, 

 second radials, interradials, orals, etc. The name inter- 

 radial was first used by DeKoninck at a time when the Blas- 

 toideae were regarded as a sub-order of Crinoideae. In 1879 

 they were regarded as homologous to the oval plates of 

 Crinoids by Wachsmuth, which statement he corrected three 

 or four years later when he called them true interradials.* 

 He says : — 



* ' The term * oral ' for the deltoid pieces was proposed by 

 Wachsmuth and Springer in Part I. of their Revision, and 

 afterwards adopted by Prof. v. Zittel and by Messrs. 

 Etheridge and Carpenter. 



** Since the publication of the present article, I became 

 fully convinced that the so-called deltoid pieces are not oral 

 plates, but true interradials, and that, as such, they form a 

 part of the abactinal system. If the deltoids were actinal 

 plates, and this they should be if they were orals, the 

 actinal regions in Elaeacrinus obovatus would extend to over 

 three fourths of the entire body — a proportion almost 

 equal to that of Echini. On the contrary, in the allied 

 Granatocrinus norwoodi, with small deltoids, and in Hetero- 

 schisma gracile, the actinal system excluding the ambulacra, 

 would be limited to a small area around the oral pole, and 

 occupy scarcely more than a twentieth part. The different 



♦ Proceedings Davenport Academy of Natural Sciences, Vol. IV., p. 76. 



