76 Br. F. A. Bather — Notes on Yunnan Cystidear 



characters about which Miller and the other American authors give 

 least information. There is one exception. Under H. subglobosus, 

 1889, Miller says that the pores are in pairs forming figures somewhat 

 like an omega, a>. This striking character was seized on by Jaekel 

 (1899, p. 413) to warrant the separation of this (as genotype) and 

 any similarly constituted species from Holocystis ( = Megacystis) 

 Hall, as a new genus Trematocystis with the following diagnosis : 

 [An Aristocystid with] " Theca irregular, pval or pyriform, attached 

 by a rather small surface. Plates fairly large and not very 

 numerous. Apparently as a rule four brachioles at the corners of 

 the peristome. Diplopores with long multifariously irregular pore- 

 passages joined to one another in groups." To this genus Jaekel by 

 implication referred all Miller's species from the Osgood and Laurel 

 Limestones, but possibly he did not mean to include II. jolietensis 

 from the Racine Limestone. 



The first question to decide is whether this character really 

 distinguished H. subglobosus Miller from II. cylindrica Hall. 

 Jaekel does not discuss this particular question, but takes the more 

 drastic action of removing all the species referred to the genus by 

 Hall, together with Saceocystis [whatever that unknown name may 

 denote], to his Cladocrinoidea [essentially Crinoidea Camerata], of 

 which he regards them as an aberrant type. He gives no reasons for 

 this step, and I have been unable to discover any. The specimens 

 from the Racine Limestone are not preserved so as to show either the 

 smaller thecal openings or the structure of the pores, since they are 

 for the most part internal casts or incomplete external moulds. The 

 surface, however, is said to be strongly granulose, and this agrees 

 with many of the species described by Miller. The specimen from 

 the Ilacine Limestone of Joliet, described by Miller, is also known 

 from internal oasts, but on these Miller detected the marks of pores 

 penetrating the pustules, as in H. papulosus. In Hall's figures the 

 pustules are clearly indicated, especially in II. abnormis. The later 

 figures of S. cylindricus and H. altematus represent the pores as 

 having a radiating arrangement (cf. 8. yunnanensis). This is also 

 noticeable in Miller's figure of II. tumidus from the Osgood Lime- 

 stone. Therefore there seems no reason to doubt that the American 

 authors are right in associating all these species. 1 



This, however, does not fully answer the question whether all the 

 species have the <w-cfiannels. Owing to the peculiar preservation of 

 the Ptacine fossils, it is not likely that direct evidence as to the 

 structure of their pores will ever be available. It is legitimate to 

 interpret them in the light of such forms as II. papulosus, 

 H. pustulosis, and H. ornatus, which have plates ornamented with 

 well-marked pustules, usually quite separate from one another. 

 Setting minor differences aside for the present, I may express my 

 conviction that these species, as well as all others from the Osgood 

 Limestone, did possess w-channels. This conviction is based on the 

 following facts. Miller's silence on the subject, except in the case 

 of H. subglobosus (1889), proves only that he attached far less 

 importance to these structures than to the number of plates and the 



1 I do not include Hall's pi. xii, fig. 6, which if correct is almost certainly 

 of a different genus. 



