80 THE SEA SHORE 



Some of the shells should be preserved with the spines all 

 intact, and others with these removed in order to show the 

 arrangement of the plates which compose the shell, as well as the 

 perforations, and the rounded processes to which the spines are 

 articulated. 



The majority of sea urchins are provided with a most com- 

 plicated and beautiful arrangement of teeth which are well 

 worthy of study. These should be removed from a moderately 

 large specimen, the soft surrounding structures carefully dissected 

 away, and then cleaned by means of an old tooth-brush without 

 disarranging them. 



It will be found that dried sea urchins will require care when 

 preserved with spines attached, for these appendages are usually 

 very brittle and are easily dislocated at their bases where they are 

 united to the shell by ball-and-socket joints. 



It may be mentioned here that corrosive sublimate is very 

 valuable for preventing the development of mould on the surfaces 

 of starfishes, sea urchins, and museum specimens generally. It is 

 best supplied in the form of an alcoholic solution made by dissolving 

 a few grains in about half a pint of methylated spirit ; the advantage 

 of this over an aqueous solution being the rapidity with which it dries. 

 In most cases it is simply necessary to apply the solution to the 

 object by means of a soft brush, but, as regards starfishes and 

 urchins it is far better to dissolve a few grains of the corrosive sub- 

 limate in the spirit in which the objects are placed previous to 

 drying. 



CRUSTACEANS 



The preservation of crustaceans by the dry method often requires 

 some care and demands a certain amount of time ; but the process 

 is never really difficult, and the satisfaction of having produced 

 a good specimen for a permanent collection well repays one for 

 the trouble taken and time spent. 



Some of our crustaceans are only partially protected by a firm 

 outer covering, and almost every attempt to preserve these as dry 

 objects results in such a shrivelling of the soft tissues that the 

 natural appearance is quite destroyed. This is the case with some 

 of the barnacles, and the abdominal portion of the bodies of hermit 

 crabs, which are, therefore, far better preserved in fluid. Dilute 

 spirit is quite satisfactory for most of these as far as the preservation 

 of the soft structures is concerned, but it has the disadvantage that 



