1896. THE PREPARATION OF CHALK FOSSILS. 307 



countless treasures, which only require to be washed in water to be 

 ready for mounting. It is very different for those who work in 

 districts where the flint is compact, for there every specimen must be 

 laboriously worked out of the chalky matrix. 



Every collector of Bryozoa must have been struck with the 

 number of beautiful forms to be found in a cliff section, which are 

 useless, by reason of the weathering of the exposed surface. The 

 dental-engine offers a very simple solution of this difficulty. The 

 process is as follows. Thoroughly clean the exposed surface with 

 the badger-hair brush, and work it so finely that the specimen is 

 nearly undercut. With a sharp pointed knife free the specimen from 

 the block, taking away the smallest possible amount of matrix with it. 

 Cement it, worn surface downwards, on some suitable rough surface, 

 and when dry work the unweathered surface with the badger-hair 

 brush. It is important to apply the gum only to the fossil itself, and 

 to leave the matrix untouched by the cement. Soak off the specimen 

 in hot water, and mount on a slip of black cardboard. An excellent 

 thing to fix the specimen upon is a glass slip that has been 

 roughened in the centre with , hydrofluoric acid. Kay's cement has 

 proved very useful in my hands. Bryozoa as thin and fragile as 

 Entalophora proboscidea and Vincularia regnlaris can be treated in this 

 fashion. In a like manner all small fossils, such as macroscopic 

 Foraminifera, little brachiopods, and small Serpulae can be removed 

 from their matrix, and mounted in any position on black cardboard. 



These instances are quoted as examples of the delicate work 

 which one can get out of the engine ; but it must not be supposed 

 that practice and deft fingers have nothing to do with the process. 

 Those who are engaged with the zonal distribution of the Bryozoa 

 will find the engine most helpful in obtaining a rapid determination 

 for making a list. If one has to handle several hundred Bryozoa 

 from one zone, it is manifestly impossible to clean them all perfectly, 

 and a few touches of the brush will put the determination beyond 

 doubt, and at the same time tell one if the specimenis worth working. 

 Bryozoa like Truncatula, Semicytis, Homcecsolen, and Idmonea require to 

 be worked on both sides to establish a determination, and in these 

 cases the rapid work of the engine is simply invaluable. 



But the dental-engine can do hard work equally well, and perhaps 

 no better chance of testing its powers could be found than the 

 effectual cleaning of large masses of Chalk-marl sponges, such as 

 Plocoscyphia labvosa, Craticularia fittoni, and all the host of intractable 

 lithistids. In this case the bristle-brush is replaced by the cutting 

 rose-headed bur, and the steel and brass brush, and it is astonishing 

 to see the way in which the hard matrix melts away before the 

 business-like little tools, and the manner in which the sponge structure 

 is revealed, but not destroyed. In fact, so much can be got out of 

 the engine, both in power and delicacy, that the results leave little to 

 be desired. Given a reasonably workable chalk, the specimen should 



