328 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 45. 



tenuistriata Hall is 10 by lOi by 6 mm. It is said to be "more finely 

 striated than the preceding," i. e., 0. nova scoticus. Our shells from 

 8.21. lA appear to have "greatest width near the middle," which agrees 

 with the original figure and is inserted in the description of the species 

 so identified from the Waldron shale. ^ Our specimens are, however, 

 very httle convex, and not noticeably, "more ventricose than C. 

 comuta of the Chnton," though considerably larger than the original 

 type as figured. 



Specimens in the Cornell University Museum (originally belonging 

 to the Jewett collection and marked " Chonetes comuta Hall" from 

 the Chnton formation New Hartford, New York, Cat. No. 2197) show 

 considerable variation in size. Dimensions of the smallest specimens 

 are 5 by 3 mm., the largest 15 by 8 mm. The radii are very similar to 

 those of Maine specimens of the same size, are in the larger specimens 

 over 100 at the margin, and the median radii are double strength, as 

 said to be characteristic of some of the specimens from Arisaig and 

 particularly of the specimens from Waldron called Chonetes nova 

 scoticus. The form of C. comuta varies but the specimens referred 

 to are none of them fully twice as broad as long, though nearly so. 



The original specimen figured by Hall of C. nova scoticus has not the 

 strong central radii, but in the text "a stronger and more elevated 

 stria," it is said, "often marks the median line from the beak to base 

 of ventral valve. "^ It is difficult to determine what morphological 

 characters belong to these specific names as used. The definition of 

 C. tenuistriata makes it to be more finely striated than C. nova 

 scoticus, also larger and more finely striated than C. comuta, but the 

 number of strise on the margin of C. tenuistriata is given as nearly 100, 

 whereas the striae are given as "more than 100 on the margin of C. 

 nova scoticus. 



The specimens in the Cornell University collection from the Clinton 

 are much more finely striate than the figures given of the species C. 

 comuta.^ The increase in number of radii is produced by dichoto- 

 mising or interstitial additions in course of growth, and hence the 

 larger the size of a given species (supposing the rate of increase were 

 uniform) the greater would be the resulting number of radii at the 

 margin. Fluctuation also takes place in the growth laterally in 

 relation to the length. 



The form I call C. edmundsi is a small species vnih the dichotomising 

 process rare, as in typical C. striatella, and the lateral growth not 

 reacliing twice the length. The form I call C. striatella attains 

 ordinarily more than twdce the dimensions of C. edmundsi, the strige 

 occasionally but rarely bifurcate except at the cardinal angles, and 



1 28th Aim. Rept. N. Y. State series, p. 155. 

 » Acadian Geol., 4tli ed., p. 59C. 

 » Pal. N. Y., vol. 2, pi. 21, fig. 10. 



