139 



A METHOD OF REMOVING TESTS FROM FOSSILS. 



S. S. BUCKMAN, F.G.S. 



The following remarks apply especially to brachiopods ; but 

 there is reason to believe that the method may be extended 

 with advantage to other classes of fossils. Among brachiopods 

 natural casts are not frequently met with, except in a few- 

 favoured localities ; and the natural casts are often unsatis- 

 factory. Therefore a method of making artificial casts by 

 removal of the tests becomes of value when it is desired to 

 study internal characters. The following is the method : 



Choose specimens which are not crystalline, and preferably 

 those which are likely to have a close-grained,* hard internal 

 core. Heat them to redness and then drop into water. Much 

 of the test will then fall off ; what remains can sometimes be 

 wholly removed by brushing. If not, the delicate use of a 

 sharp penknife will separate the rest. Care must be employed 

 in using the penknife to prevent scratching of details of muscle 

 marks, ovarian area, or vascular markings. 



Heating may be done in the ordinary fire, but it is not alto- 

 gether satisfactory ; the specimens may be burnt too much. 

 Heating by means of a bunsen flame, or a spirit lamp, or for 

 larger specimens a gas or spirit blow-lamp, is more satisfac- 

 tory. As the test is more adherent over the muscle areas, they 

 should be heated most ; that is, the specimens should be held 

 beak downwards in the flame in the case of brachiopods. 



Experiments so far have been chiefly with Mesozoic brachio- 

 pods, and of these the Rhynchonellids come out most satisfac- 

 torily, presumably on account of their fibrous test : some of 

 them make very beautiful casts, showing all details excellently, 

 but, of course, much depends on the state of fossilization. The 

 Dallininae have also yielded satisfactory results, but for some 

 reason the Terebratulids do not come out so well, and the pro- 

 portion of spoilt specimens is considerable. 



In the case of rare specimens, the method should only be 

 enployed after careful consideration : there is, of course, a risk 

 of destroying the specimen altogether ; and in any case details 



* When this note originally appeared, in the ' American Journal of 

 Science,' XXXII. 163, Aug. 1911, the epithet ' close-grained ' was printed 

 ' coarse-grained ' by some accident, and I did not see any proof. How- 

 ever, it is obvious that a coarse-grained core is the last thing that would be 

 desirable. A hard core has a grain of close and fine texture, and that is 

 what is required. A coarse-grained core is the sort of thing met with in 

 some of the Lower Oolites, where the rocks are trulj^ oolitic ; and such a 

 core, if it does not crumble away when heated, will yield no muscle-impres- 

 sions of any value. A coarse-grained core is found in fossils from some 

 of the siliceous sands, like the Greensand : it may be coarse-grained and 

 incoherent, so that on the removal of test everything crumbles away. 

 But calcareous sands, and also clays, often yield specimens (Brachiopods) 

 with good cores of close texture. — Note by Author, March 1912. 



iqi2 May i. 



