Raymond — Trilobite Retaining Color-Markings. 463 



the tests of many trilobites being rather thick and cal- 

 careous, it may be possible to predict various shades of 

 orange in their coloration. With an appropriate organic 

 base the red lipocrome apparently produces a blue 

 compound, which with the yellow and red produces green 

 and brown. With the aid of these general principles 

 and applying previously gained knowledge of the prob- 

 able habits of any particular form, it may be possible 

 to approximate somewhat reasonably to the actual 

 appearance of one of these animals in nature. 



Trilobites usually possess colors which are obviously 

 considerably influenced by the nature of the sediment 

 in which they are imbedded, and since carbon and its 

 compounds or oxides of iron are the most common color- 

 ing agents in the rocks, the specimens are usually from 

 rusty brown through dark gray to black. A light- 

 colored limestone would seem to be the most favorable 

 matrix for the preservation of original colors, for in this 

 case there would probably be only loss of pigment, with- 

 out much chance of substitution except where recrystalli- 

 zation has taken place. A number of light-colored 

 limestones yield fossils, and I have always felt that there 1 

 must be some significance in the fact that the trilobites 

 of the Maquoketa of Iowa, the Upper Ordovician of 

 southern Ohio and Indiana, and the Lower Ordovician 

 of the Ladoga region east of Petrograd were all of about 

 the same color. On the best preserved specimens from 

 which the matrix has been chiseled away the color is a 

 rich chocolate-brown, whereas the ones which have 

 weathered out naturally are usually much lighter, rang- 

 ing toward yellow or cream-colored. It seems entirely 

 possible that both red and yellow pigments may have 

 entered into the composition of the original coloring 

 matter of these specimens. The fact that all the trilo- 

 bites of these localities, whatever the family, show the 

 same chromatic characteristics may indicate one of three 

 things ; that the color is really in some way due to the 

 composition of the matrix ; or, that only the basic colors 

 have left traces ; or, that the Ordovician trilobites were 

 rather uniformly colored and exhibited only shades of the 

 primitive red which is dominant among crustaceans at 

 the present time. Trilobites from the light-colored lime- 

 stone of the Silurian of Indiana, England, and Bohemia, 



