84 PROCEEDINGS OF THE ACADEMY OF [1886. 



them was rather peculiar. According to his diagnosis, the calj'x 

 of Haplocrinus is composed of five basals. These, as he states, 

 alternate with five " para-basals," of which three are separated 

 from the basals by intervening plates (Costalglieder). H& 

 states further that, placed upon the sutures of two adjoining 

 " para-basals," there are five simple arms, which in their closed 

 condition form a pentamerous " Scheitelpjn-amide." If it were 

 true that the latter plates, which at their lateral union form con- 

 spicuous grooves, were arras, this Crinoid would have no radials, 

 and the basals would be radially disposed, contrarj^ to the funda- 

 mental rules of the class. The ventral pyramid had been errone- 

 ously described by Goldfuss as composed of five series of eight 

 to ten pieces longitudinally arranged, and it was this, likely, 

 which misled Roemer. The fact, however, is that the ventral 

 surface is covered by five single trigonal pieces, arranged alter- 

 nately with the upper ring of plates in the dorsal cup, and that 

 the latter plates, as Goldfuss correctly stated, are provided with 

 an articular facet upon which the arms moved. This was con- 

 firmed by Miiller's observation, who, in 1855, discovered in one of 

 his specimens, resting upon the facet, a small brachial. 



Allman was the first writer who undertook to homologize the 

 five ventral plates of Haplocrinus, Goccocrinus and Stephanocri- 

 nus with the orals of recent Crinoids. It seems, however, that he 

 was not aware of Miiller's discover}^ of arm joints, for he supposed 

 that all those genera possessed recumbent ambulacra. A similar 

 view was held by d'Orbigny, Schultze calls the ventral plates 

 " interradiale Pyramidenstiicke." Zittel describes the " Kelch- 

 decke " to be composed of " fiinf grossen, im Centrum zusammen- 

 stossenden, dreieckigen Oral-platten, welche eine Pyramide bilden, 

 und zwischen sich fiinf breite, gerade, durch die abgeschragten 

 Seitenflachen begrenzte,nach unten geschlossene, nach oben oflfene 

 Ambulacralfurchen bilden." There is nothing to confirm this 

 view, and, in fact, we do not know how this could have been 

 possible. It is difficult to see what office the so-called " open 

 ambulacral groove " could have had, especially if Haplocrinus 

 possessed arms, as Prof. Zittel admits. The grooves, evidently, 

 are mere compartments for the reception of the arms, and served 

 for their protection. Carpenter agrees with Zittel that the ven- 

 tral plates are orals, but opposes his open ambulacra. He regards 

 the o-enus to be " permanently in the condition of a Pentacrinoid 

 larva with a closed tentacular vestibule." We fully agree with 



