THE OTTAWA NATURALIST. 



Vol. XX. 



OTTAWA, AUGUST, 1906. 



No. 



THE SPECIES OF BOTRYOCRINUS. 



By F. A. Bather, British Museum 'Nat. Hist.), London, S.W., England. 



Twelve years have passed since the first publication of a 

 statement that Rotryocrinus occurs in America ' Crin. Gotland,' 

 Svensk. Vet.-Akad. Hatidl., XXV. No. 2, pp. 103-105 ; 1893. 

 Although two of the determinations there made have been accept- 

 ed by such well-known palaeontologists as Dr. J. F. Whiteaves 

 and Dr. Stuart Weller, the facts appear to be still unrecognized 

 by some American writers on fossil crinoids. It may therefore be 

 useful to consider the generic position and the specific independ- 

 ence ol the alleged American forms more fully than heretofore. 



Comparison of the American species, rightly or wrongly re- 

 ferred to Botryocrinus, with the species found in Europe and Aus- 

 tralia is rendered difficult by the fact that the diagnoses of the 

 latter were based mainly on the characters of the arm-structure 

 and partly on those of the stem-structure, whereas the former 

 species are represented only by dorsal cups. It has, therefore, 

 been necessary to re-study the dorsal cups of the European and 

 Australian species and to prepare diagnoses founded on those 

 elements alone. While the European and Australian species are 

 not readily distinguished inter se upon these grounds, the dorsal 

 cups of the American species fortunately present more points of 

 difference. 



My thanks are due to Dr. Whiteaves for kindly lending me 

 the unique specimen of his Homocrtnus crassus, of which a plaster 

 cast is now preserved in the British Museum ; also to Mr. F. 

 Chapman of Melbourne for sending a wax squeeze of his Botryo- 

 crinus longlbrachiatus to the same museum. A re-examination of 

 this and other material contained in the British Museum has 



