May, 1017 



Silurian Fossils from Ohio 



235 



Jaekel's genus, Trematocystis. The remainder belong to closely 

 allied genera. None belong to true Ilolocystites. 



There is no evidence that Ilolocystites ovatiis, II. scutellatus, 

 II. winchelli, II. sphcericus, or //. jolietensis, from the Racine of 

 Wisconsin and Illinois, are closely related to the Osgood forms 

 of Trematocystis. Although apparently not congeneric with 

 Ilolocystites as here defined, they nevertheless may prove 

 closelv related. 



Hallicystis imago, Hall. Plate XI, Fig. 2. 



The type of Apiocystites imago, Hall, numbered 2025, is 

 preserved in the American Museum of Natural History, in New 

 York City. It is figured in the Twentieth Report of the New 

 York State Cabinet of Natural History, on plates 12 and 12a, 

 and the arrangement and outline of the plates has been dia- 

 grammed by Schuchert in his paper On Siluric and Devonic 

 Cystidea and Comarocrinns, published in the Smithsonian Mis- 

 cellaneous Collections in 1904. No occasion for further com- 

 ment on the type specimen would remain were it not for the 

 fact that it presents certain features not noted in any of the 

 preceding studies. 



Fig. 1. Plate diagram of type of Hallicystis imago, Hall. The dotted lines 

 crossing the plates indicate the direction of the faint angulations. The double 

 character of plate 23 can not be determined from this type. 



In studies of the CaJlocystidcc it is evident that plate 3 sup- 

 ports plates 7, 8, and 9, and thus takes the place of two plates, 

 one alternating with the bases of plates 7 and 8, and the other 

 alternating with the bases of plates 8 and 9. This is true also 

 of the specimen of Ilallicystis imago diagrammed by Schuchert 

 in the publication cited above. 



