6 THE APPENDAGES, ANATOMY, AND RELATIONS OF TRILOBITES. 



time was devoted in the main to its solution by preparing these trilobites and learning their 

 anatomical significance. 



The specimens of Triarthrus becki from Rome are pseudomorphs composed of iron 

 pyrites, as has been said, and are buried in a gray-black carbonaceous shale. A little rub- 

 bing of the specimens soon makes of them bronze images of the former trilobite and while 

 under preparation they are therefore easily seen. However, as the average individual is 

 under an inch in length and as all the limbs other than the antennre are double or biramous, 

 one lying over the other, and the. outer one fringed with a filamentous beard, the parts to 

 be revealed by the preparator are so small and delicate that the final touch often obliterates 

 them. These inherent difficulties in the material were finally overcome by endless trials on 

 several thousand specimens, each one of which revealed something of the ventral anatomy. 

 Finally some 500 specimens worthy of detailed preparation were left, and on about 50 of 

 these Beecher's descriptions of Triarthrus and Cryptolithus were based. 



The black shale in which the specimens are buried is softer than the pseudomorphous 

 trilobites, a condition that is of the greatest value in preparation. With chisel and mallet 

 the trilobites are sought in the slabs of shale and then with sharp chisels of the dental type 

 they are revealed in the rough. At first Beecher sought to clean them further by chemical 

 methods, and together with his friends, the chemist Horace L. Wells, and the petrologist 

 Louis V. Pirsson, several solutions were tried, but in all cases the fossils were so much 

 decomposed as to make them useless in study. Therefore Beecher had to depend wholly oh 

 abrasives applied to the specimens with pieces of rubber. Much of this delicate work was 

 done on a dental lathe, but in the final cleaning most of it was done with patient work by 

 hand. Rubber has the great advantage of being tough and yet much softer than either speci- 

 men or shale. As the shale is softer than the iron pyrites, the abrasives (carborundum, 

 emery, or pumice) took away the matrix more quickly than the trilobite itself. When a 

 part was fully developed, the rubbers were cut to smaller and smaller dimensions and the 

 abrading reduced to minute areas. So the work went on and on, helped along from time to 

 time by the dental chisels. Finally Beecher became so expert with these fossils that after 

 one side was developed he would imbed the specimen in Canada balsam and fix it on a glass 

 slide, thus enabling him to cut down from the opposite side. This was done especially with 

 Cryptolithus because of the great scarcity bf material preserving the limbs, and two of these 

 revealed both sides of the individuals, though they were then hardly thicker than writing 

 paper. 



Then came illustrations, which at first were camera-lucida drawings in pencil smoothed 

 out with pen and ink. "In some quarters," however, it has been said, "his methods unknown, 

 their results were not accepted; they were regarded as startling, as iconoclastic, and even 

 unreliable." He therefore decided to rework his material and to illustrate his publications 

 with enlarged photographs. The specimens were black, there was little relief between fossil 

 and matrix, and the ammonium chloride process of coating them white and photographing 

 under artificial light was unsuitable. Nevertheless, after many trials, he finally succeeded 

 in making fine enlarged photographs of the trilobites immersed in liquid Canada balsam, with 

 a contact cover of glass through which the picture was taken, the camera standing vertically 

 over the horizontal specimen. Beecher had completed this work in 1903 and in the winter of 

 1903-1904 was making the drawings, nearly all of which are here reproduced. On Sunday 

 morning, February 14, 1904, as he was working at home on a large wash drawing of Cryp- 

 tolithus, death came to him suddenly, leaving the trilobite problem but partially solved. 



