CAMBRIAN HOLOTHURIANS 1 



AUSTIN H. CLARK 



Preface. — In a recent number of Science 2 Dr. Hubert 

 Lyman Clark published a most interesting and valuable 

 summary of the literature on the fossil remains of the 

 Holothuroidea, accompanied by critical remarks. The 

 greater part of his paper is devoted to a consideration of 

 Dr. Charles D. "Walcott's contribution to the knowledge 

 of Cambrian geology and paleontology in which there 

 are described as holothurians, under the new generic 

 names Eldonia, Laggania, Louisella and Mackenzia, four 

 new forms from the Middle Cambrian of British Colum- 

 bia. 3 



Dr. Clark reaches the conclusion that Laggania can 

 not positively be assigned to any invertebrate phylum, 

 for he sees 1 'nothing beyond the probable form of the 

 body, and the terminal mouth, to suggest a holothurian, 

 and these characters are equally suggestive of actini- 

 ans;" Louisella he does not believe is a holothurian, 

 though he can offer no suggestion as to its proper sys- 

 tematic position ; Mackenzia he does not consider a holo- 

 thurian; he hints that it may be an actinian, though he 

 hastens to emphasize the fact that he does not positively 

 make that assertion; Eldonia he is sure is not a holothu- 

 rian, but he does not place it in any phylum. 



To sum up Dr. Clark's criticism, he is sure that none 

 of the four genera established by Dr. Walcott really 

 belong to the Holothuroidea, but he is quite unable to 

 suggest a more logical resting place for any of them. 



1 Published by permission of the secretary of the Smithsonian Institution 

 who, however, does not hold himself responsible for any of the views 

 expressed. 



7 Science, Vol. 35 (N. S.), No. 894 (February 16, 1912), p. 274. 

 s Smithsonian Miscellaneous Collections, Vol. 57, No. 3, pp. 41-58. 

 488 ' 



