SMITHSONIAN EXPLORATIONS, I929 I3 



proved a kind friend in a strange country and particularly with a 

 strange language. Due to his generous help, the work of casting the 

 echinoderms was completed earlier than anticipated and I was ahle to 

 spend some time in similar work upon the equally interesting trilohites 

 and other groups of fossils. 



It may be of interest to review the methods used in preparing these 

 casts. In many instances the specimen is represented only by a mould 

 in the rock — that is, a cavity once occupied by the fossil which has 

 since been dissolved away. Barrande's illustrations of such specimens 

 were made from guttapercha squeezes of the moulds, but. due to the 

 better quality of material today, the squeezes now prepared prove even 

 better copies than the figured types themselves. Whenever the actual 

 fossil is preserved, an impression, or, in other words, a mould is made 

 by first dusting the specimen with talcum powder and then pressing 

 plastocene or modeling clay upon it. To save time, these impressions, 

 carefully packed in pasteboard boxes to prevent distortion, were 

 shipped to Washington where plaster of paris casts are now loeing 

 made from them. This method of casting not only gives excellent 

 results in showing detail, but is the safest means to employ for delicate 

 specimens such as the trilobites in the Barrande collection. The 

 lower half of figure 6 shows the delicacy and interesting variety of 

 some of these trilobites while the upper portion illustrates some of 

 the curious cystid types which comprise a large part of the Barrande 

 echinoderm collection. 



The Paleozoic rocks of Bohemia outcrop in a syncline or down fold 

 which, in the vicinity of Prague, is cut through by the Moldau River, 

 thus aft'ording numerous natural exposures. These rocks contain an 

 abundance of fossils which have long attracted attention. The first 

 geological work of note in the region, however, was accomplished by 

 Joachim Barrande who made Bohemia classic ground for the study of 

 ])aleontology. Born in France in 1799 and educated in the Ecole 

 Polytechnique at Paris as an engineer, Barrande's first appointment 

 was that of tutor to the grandson of Charles X, the Due de Bordeaux, 

 who was afterwards known as Comte de Chambord. When the king 

 abdicated in 1830, Barrande accompanied the royal family to England, 

 thence to Scotland, and finally to Bohemia, where at Prague he took 

 up engineering work. In the course of this pursuit, his attention was 

 called to the Paleozoic fossils of the region, and with the publication 

 of Murchison's Silitriaii Sysfeiu in 1839, he was led to make a study 

 of the supposed equivalent strata in Bohemia. He entered into this 

 work on such a large scale, engaging many workmen to open up quar- 

 ries and collect fossils, that he finally acquired an unrivaled collection 



