48 The Ohio Journal of Science [Vol. XXI, No. 2, 



Use of Term Lysocystites. — Since the generic name 

 Lysocystites was proposed in 1889, five years earlier than 

 Aethocystites, the latter is abandoned. 



Relationship. — Lysocystites was referred by Bather (The 

 Echinoderma, 1900, p. 70) to the CryptocrinidcB, the sole family 

 of the Aporita. The relationship is even closer than hitherto 

 suspected. In Cryptocrinus, from the Ordovician of Russia, 

 there are three basal plates formed by the fusion of two pairs of 

 the original five, the unfused plate being in the right anterior 

 interradius. Alternating with the five original basal plates is a 

 second series of five plates, all free from each other and hexa- 

 gonal in outline, followed in turn, in alternating order, by a 

 third series of five plates, subpentagonal in outline. The anus 

 lies between two plates of the third series, separated from the 

 nearest plate of the second series by a small supplementary 

 plate. In all of these features Cryptocrinus closely resembles 

 Lysocystites. The latter differs chiefly in the more elevated 

 position of the anal aperture, the latter being located at the top 

 of the third series of plates rather than between two of the 

 latter. None of the plates of the fourth series, nor any of the 

 tegminal plates at the extreme summit of the theca, are known 

 in case of Lysocystites. 



Holocystites Hall. 



Holocystites Hall, 20th Rep. New York State Cab. Nat. Hist., 1868. p. 311, 380. 

 Genotype: Holocystites cylindriciis Hall. 



Megacystites Hall, Addenda of preceding report, p. 380. Substitute for 

 Holocystites. 



Trematocystis Jaekel, Stammesgeschichte der Pelmatozoen, 1899, p. 414. 

 Genotype: Holocystites subglobosus (Miller), PI. 4, Fig. 2. 



Holocystites of Hall. — The genus Holocystites was founded by Hall 

 on six species of cystids which agreed in having the plates arranged in 

 more or less alternating transverse or more or less alternating vertical 

 rows, the plates of the more primitive species showing a marked tendency 

 toward a predominance of hexagonal outlines. The oral aperture was 

 terminal and the anal aperture was eccentric but only a short distance 

 away from, the oral one. The arms evidently were not recumbent and 

 there was no trace of their former location. 



The first three species described in the accompanying text agreed in 

 being distinctly elongated in a vertical direction, the first species of this 

 series being called Holocystites cylindricus on this account. In reality, 

 three forms are figured under this name, of which figure 4 on plate 12 

 is regarded here as the type. The second described species, Holocystites 

 alternatus, differs from the first by the intercalation of numerous sup- 

 plementary plates between the transverse rows of more primitive plates. 



