KNOWLTON : FOSSIL TURTLES 65 



taceous age of the Lance formation ("Ceratops beds")- In the 

 present paper the several species of turtles accredited to the 

 Judith River formation are passed in critical review so far as 

 regards the type locality and formation for each and its sub- 

 sequent published distribution, both areal and vertical. The 

 following conclusions are reached: (1) The Judith River fauna 

 has had accredited to it at least sixteen species of fossil turtles. 



(2) Of these sixteen species seven are to be excluded on the suffi- 

 cient ground that they do not occur in beds of Judith River age. 



(3) Of the nine remaining species that may have a more or less 

 valid claim to membership in the Judith River fauna, five have 

 their type localities in beds of Judith River and Belly River age 

 and four in horizons above that of the Judith River. (4) Of the 

 five typically Judith River species, four are absolutely confined 

 to these beds, while the remaining one which has an alleged higher 

 range is shown to be probably a composite species, possibly includ- 

 ing three species which correspond respectively to the three hori- 

 zons involved. (5) Of the four species, the types of which came 

 from post-Judith River beds, and which are claimed to range 

 downward into the Judith River, not a single one has a clear title to 

 be so regarded. (6) It is plain, then, that the comparisons that 

 have been made between "Judith River" turtles and those of 

 higher horizons (Lance formation, "Laramie," "Ceratops beds," 

 "Hell Creek beds," "somber beds," etc.), have not beenmade 

 with species that really belong to the Judith River fauna, but 

 with forms that actually belong to these higher beds. It is not 

 to be wondered at that such a comparison has resulted in show- 

 ing "identity" and "striking similarity." 



ZOOLOGY. — Remarks on the nervous system and symmetry of the 

 crinoids. Austin H. Clark, U. S. National Museum. 

 Communicated by Barton W. Evermann. 



A year ago I published {American Naturalist, vol. 44, p. 243) 

 a short note in which I showed how the nervous system of the 

 crincid might have originated from a nervous system of the 

 annelid-arthropod type concurrently with a loss of directive 

 motion. It remains to be indicated, however, in what way the 



