364 NATURAL SCIENCE. June, 



F. A. Bather, whose results are published in the last number of the 

 Proceedings of the Zoological Society (vol. for 1895, PP- 974 -I >° 4> 

 pis. liv.-lvi.). A restoration there depicted shows Uintacrinus swim- 

 ming about in swarms, with ten arms, each over 3 feet in length. 

 These arms contain numerous syzygies, or brittle immovable unions, 

 between their ossicles, indicating points at which the arms could 

 readily be broken off if they became entangled in those of other 

 individuals. But the most interesting part of the paper is that which 

 discusses the affinities of Uintacvinus. It is pointed out that the 

 absence of a stem is a feature common to genera drawn from diverse 

 groups. Marsupites, Saccocoma, and Uintacrinus are three genera that 

 have no trace of a stem or of any anchoring organs, but in other 

 respects are of dissimilar structure. The points in which they resemble 

 one another, viz., the large size of the calyx, and the presence of a 

 centrale, are therefore held to be secondary features. The essentials of 

 structure in Uintacvinus being determined, it is shown that they are 

 quite different from those of all crinoids with which previous writers 

 had connected the genus. On the other hand, the resemblances to the 

 Pentacrinidae lie in essentials, and the main difference — the intercala- 

 tion of interbrachial plates — is of a secondary nature. The author 

 maintains that the Triassic pentacrinid, Dadocrinus, possesses just 

 those features which must have been possessed by the ancestor of 

 Uintacrinus, and also shows a tendency to the intercalation of tegminal 

 plates between the arms. Uintacrinus, he concludes, is descended 

 from the palaeozoic Crinoidea Inadunata, and branched off from the 

 ascending line that contains Encrinus, Dadocrinus, Pentacvinus, and 

 Apiocrinus. 



The moral of the paper seems to be that more detailed know- 

 ledge is needed about forms that we are supposed to know fairly 

 well, and that speculation is useless until such knowledge is gained. 

 We hope that Mr. Bather may be able before long to complete the 

 studies which, he hints, he has long been making on Marsupites. 



A New South American Mammal. 



It is notoriously difficult to understand the relationships among 

 living and extinct marsupial animals. No doubt marsupials represent 

 the highly modified and divergent descendants of a decaying group, 

 and it might be expected that the gradual discovery of the remains of 

 extinct forms would lead to a better understanding of the modern 

 relics of the group. Up to the present time, however, the palaeonto- 

 logical discoveries have not made the questions simpler, and Mr. 

 Oldfield Thomas' account (Proc. Zool. Soc. London, 1895, p. 870 J of a 

 newly discovered American marsupial, has added, in a very unusual 

 fashion, to the interest and to the difficulties of the question. If we 

 accept Mr. Oldfield Thomas' view that syndactylism is a character 

 that may have been acquired secondarily by different sets of 



