1879.] NATURAL SCIENCES OF PHILADELPHIA. 227 



ontologists, but b}' some entirely ignored. It is a singular fact 

 that European authors have commonly refused to accept our 

 genera of Actinocrinidse, while they sustained those of the Cya- 

 thocrinidae, which are certainly no better defined. This is doubt- 

 less due to the fact that in Europe the Actinocrinidae do not 

 abound in such wonderful variet}' as in this country. If our 

 European brethren had to deal with nearly 300 species, as we 

 have, they would perhaps be more ready to accept our divisions. 



As early as 1842 T. Austin and T. Austin, Jr. (Rec. & Foss. 

 Crinoidea), undertook to subdivide the Crinoidea into families, but 

 they were not vei'y successful, as they placed together types of 

 very distinct groups. Roemer (Letluea Geognostica, 1855, 3d 

 Ausgabe) made another attempt in the same direction. He was 

 the first author who pointed out correctly the relations of the 

 Blastoids and Cystideans with the true Crinoids ; and, if he was 

 not so fortunate in establishing his families, we must consider 

 how imperfectly Crinoids were known at that time. Some of 

 Roemer's family names are still in use, but scarcely two of our 

 present authors interpret them alike. 



The late Prof. Angelin 1 divided the Silurian Crinoids of Sweden 

 into four sections : Trimera, Tetramera, Pentamera, and Poly- 

 mera. A subdivision according to the number of basal plates 

 may facilitate elemeutary studies, but it is certainly not a natural 

 classification. Genera which are evidently intimate^' related 

 for instance, Platycrinus and Dichocrinus, Melocrinus and Rho- 

 docrinus are thereby widely separated, while very distinct types, 

 such as Phodocrinus and Poteriocrinus, are brought together. 

 Angelin arranged his 40 genera of Swedish Crinoids under 23 

 families ; but, as he gave no diagnoses of them, we are at a loss 

 to know upon what principle his families were established. 



In the second part of an article on the " Internal and External 

 Structure of Paleozoic Crinoids," by Chas. Wachsmuth, published 

 in the August and September numbers of the Amer. Journ. Sci., 

 1877, one of the writers gave a minute description of the summit 



1 In the Iconographia Crinoideorum in stratis Suecice Siluricis fossilium, 

 auctore N. P. Angelin, opus posthumum edendum curavit Regia Academia 

 Suecise, cum tabulis XXIX. This is one of the finest illustrated works on 

 Crinoids that has ever been published, and it must be regarded as a great 

 loss to science that the distinguished author died before the completion of 

 his work. 



