86 NEW YORK STATE MUSEUM 



fact that all three specimens which show both sides equally exhibit 

 the banded upper and the white underside speaks for an actual 

 color differentiation. Still more so does the fact that in specimens i 

 and 2 the fine surface sculpture is equally well preserved on both the 

 upper and under sides, thereby refuting the possibility of a stronger 

 weathering of the uncolored side by temporary postmortem exposure. 

 In specimen 3, where weathering and etching of the white intervals 

 between the color bands has set in, both these and the underside 

 lack the fine surface sculpture through secondary processes. Speci- 

 men I shows directly by the narrow segment (see text figure 23) 

 with secondary crystallized calcite filling, which side happened to be 

 the uppermost during entombment. This side which alone preserves 

 the original brown color tint of the color bands belongs half to the 

 dorsal and half to the ventral side. This shell came hence to rest on 

 its lateral side during the entombment and ^it is the upper or exposed 

 side that preserves the color banding most completely. 



3 Would not the shell when ground near the oldest and most 

 sensitive point, the apex, show traces of wear? The specimens with 

 color banding at present available do not retain the apex. Specimen 

 2, which retains the youngest portion of these shells, is fractured 

 still 45 mm from the apex. At the point of fracture, however, where 

 it is but 5 mm wide, it retains the fine surface sculpture on all sides 

 in the most perfect manner. 



We thus see that the further facts brought out by the questions 

 raised, rather help to corroborate the conclusion of the primary dif- 

 ferentiation of the color banding on the ventral and dorsal sides of 

 Geisonoceras tenuistriatum. 



It is quite probable that also other species of Orthoceras with color 

 banding possessed this only on one side. This is, at least, suggested 

 by the specimen of Orthoceras trusitum Clarke and Rue- 

 demann, from the Guelph limestone at Rochester and now in the 

 New York State Museumi, mentioned op. cit. by Doctor Foerste. In 

 this the extremely narrow and crowded brown lines (nine to ten 

 in a width of 3 mm) are also seen only on one side. They are, how- 

 ever, also there preserved only in certain patches and thus might 

 well have been destroyed on the remaining parts of the surface. The 

 same is true in regard to the other specimens among Clarke & Rue- 

 demann's types which exhibit traces of color bands. Of these that 

 of plate 13, figure 9, retains the fluting resulting from the weather- 

 ing of the interspaces of the color bands, as far as the brittle speci- 

 men could be worked out, also only on one side. The type of the 

 specimen of plate 12, figure 4, has on account of the longitudinal 



