REPORT OF THE DIRECTOR I919 81 



In Orthoceras trusitum Clark and Ruedemann, from 

 the Guelph at Rochester, New York specimens occasionally show 

 color banding. In the specimen represented by figure 2 on plate 

 13 of Memoir 5, New York State Museum, 1903, there are nine 

 or ten vertical light brown bands in a width of 3 mm. In the 

 specimen represented by figure 9 the structure usually accompany- 

 ing color banding is present, but there is no distinctive color here. 

 This structure consists in the space between the color bands being 

 composed of a less dense and more readily weathering material than 

 that forming the color bands. 



In all cases of color banding observed by the writer the color 

 banding consisted of various tints of brown. 



The present writer has before him four splendidly preserved shells 

 of a Geisonoceras from the Trenton limestone, that retain the color 

 markings. Two of these were taken from a block of dark-gray, 

 very fossiliferous limestone obtained at Watertown, N. Y., and the 

 two others came from the very dark-gray, highly fossiliferous upper 

 Trenton limestone at Middleville, N. Y. The former appear to 

 retain even the original color. These specimens have been known to 

 the writer for many years and they were kept with material to be 

 used in a monograph of the cephalopods of the Trenton group. 



This form, before us, has been described by Hall (1843, P- 205, 

 209) both as Orthoceras strigatum and E n d o - 

 ceras proteiforme var. tenuiitexum. In the 

 former case the surface has been weathered between the darker color 

 bands leaving the latter as " the flexuous elevated longitudinal lines " 

 which gave the form its name; in the latter the extremely delicate, 

 cancellated surface sculpture is preserved and the color bands lost. 

 The name O. strigatum would have the right of priority by 

 virtue of its earlier description in Hall's work according to the strict 

 application of the rules of priority, but in this case it would lead to 

 the retention of a distinct misnomer, for the strigate or fluted char- 

 acter of the surface is but the result of weathering. We will there- 

 fore retain the better known name Geisonoceras tenui- 

 t e X t u m (Hall) for the species. 



The character now, which to us is the most important at present, 

 is the presence of the color bands on one side of the conch only. In 

 the specimen reproduced in text figure 21, which has a diameter of 

 16 mm, the color bands number 17, are .5 mm wide, brown and 

 separated by interspaces, averaging .4 mm. Toward the side the 

 bands become more widely separated, the last interspace being .9 mm 

 wide, and then they end abruptly. The interspaces in the banded 

 region are also decidedly darker (light brown) than in the bandless 



