ON A NEW GENUS AND SPECIES OF BLASTOIDS. 77 



would be of great advantage to science if they were universally adopted 

 by future writers upon Blastoids. In order to give this terminology a 

 wider circulation, and for the better comprehension of the succeeding 

 descriptions, I give here an abstract of their principal terms : 



The ''calyx" according to Etheridge and Carpenter, is composed of 

 the "Ixisals" the "radials" or forked pieces, and the "orals"* or deltoid 

 pieces. The suture between basals and radials is the " basi-radial 

 suture;" the more or less strongly marked ridge at the median line of 

 each oral is the ''oral ridge"\ In the fork-shaped radials, the handle of 

 the fork is the "body" of the radial, the two prongs are the "limbs;" 

 between the limbs is the " radial sums" which is occupied by the "aiu- 

 bulacrwn." Of the ambulacral structures, which together fill up the 

 radial sinus to a greater or less extent, the most imi^ortant is the 

 "laucet-piecc" which is excavated lengthwise by the "/ood-i:;roove" or am- 

 bulacrum i)roper. Ui)on or against it rest the "side-plates" pore-pieces 

 of Roemer; they are marked by minute pits, the "pinnule pits" or 

 sockets, which must not be confounded with the marginal pores or 



*The term "orals" for the deltoid pieces was proposed by Wachsmuth and Sprintjer in 

 Part I. of their Revision, and afterwards adopted by Prof. Zittel and by Messrs. Etheridg-e 

 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 abac- 

 tinal system. If the deltoids were actinal plates, and tliis they should be if they were orals, the 

 actinal reg^ions in Elearrimux ohovatiis would extend to over three-fourths of the entire body — 

 a proportion almost ecpial to that of Echini. On the contrary, in the allied Granatorriuus 

 Norivoodi, with small deltoids, and in Heteroschisma 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 proportions of the actinal and abactinal regions among Echinoderins were 

 looked ui)on by Prof. L. Agassiz as determining the different outlines of the various " orders of 

 this class," and he has ranked these orders according to the greater |)reponderance of the one or 

 the other of the two regions. In the Neocrinoidea, the oral and aboral regions are proportioned 

 almost equally, and this is the case not only in the adult, but is to be observed already in the 

 Pentacrinoid-larva. In the Pah-cocrinoidea, the abactinal regions, as a rule, are considerably 

 contracted, and in the lower organized Blastoids they are reduced still more. Plates of such 

 enormous dimensions as are found occasionally among the deltoids, cannot possibly form a part 

 of the actinal system in so low a group as the Blastoids, and hence cannot be orals. That they 

 are true interradials is proved by the relative position which they occupy to the interradials of 

 the Palaocrinoidea;. Like those plates, they rest upon the upper sloping sides of the radials, 

 and extend, whether consisting of a single plate as in the Cyatliocrinid<c, or of a series of pieces 

 as in Actitiocrinidce and li/ioJorrinidm, into the ventral side, to a series of plates, which were 

 designated by W. and Sp. as central piece and proximals. All of these latter plates are actinal 

 pieces, and it is evident, if the oral of the Neocrinoidea are at all represented in the Blastoids, 

 that they must be contained among their number. Whether they were represented, and by 

 which of those plates, are questions which cannot be answered within the limits of a note. The 

 discussion of these questions I must leave to the third part of the Revision, in which the oral 

 plates generally will receive special attention. 



■f It is self-evident that the " oral ridge " of Ether, and Carp, should be called the ititerradial 

 ridge. 



