422 Alger on the Identity of 



EXPLANATION OF FIGURES. 



Fig. 1 . Animal removed from the shell, organs in situ ; a a the collar ; b b respira- 

 tory sack ; c kidney ; d termination of the respiratory sack ; e e liver. 



Fig. 2. Digestive organs ; a a buccal pouch ; & oesophagus ; c c salivary glands 

 and ducts ; d membranous stomach ; e gizzard ; J" bile-duct ; g g lobes of the 

 liver ; h h intestine ; i dilatation at its commencement ; k retractor muscles of the 

 mouth. 



Fig. 3. Kidney; a kidney surrounded by the vessels ramifying on the surface of 

 respiratory sack ; b excretory duct ; c terminal portion of intestine. 



Fig. 4. Nervous system ; a upper tentacle ; b and c middle and lower tentacles ; d 

 supra- oesophageal ganglia; e commissures between the last and infra-oesophageal 

 ganglia ; J" filamentary commissure uniting small ganglia g with the superior 

 ganglia. 



Fig. 5. Organs oj" generation ; a testis ; 6 vas deferens; c oviduct; doYary; e 

 vesicle ; y continuation of vas deferens ; g penis ; h retractor muscle ; i common 

 receptacle ; k k duct of the vesicle or spermatheca ? 



ART. XXXVI. — BEAU3I0NTITE AND LINCOLNITE IDENTICAL 

 WITH HEULANDITE. By Francis Alger. Read October 5, 1843. 



There is a too prevalent disposition among mineralogists, as 

 well as among the cultivators of other departments of natural 

 science, to add something new to the catalogue of species. 

 They make specific differences in many cases where, by a 

 fuller investigation, or a nicer comparison of the object with 

 that which most nearly resembles it, an identity might be at 

 once established between them, and the science not be bur- 

 thened with so many new names. The truth of what I now 

 say, has been shown by the recent examination of several 

 minerals, accredited as new, which have been found, by some 

 of the German and Swedish chemists, to be varieties of other 

 species, or in some cases, mere mechanical mixtures. A very 

 frequent source of these mistakes, so far as mineralogy is con- 

 cerned, is owing to a scrupulous regard not being paid to the 

 chemical composition of the substance ; this being the essen- 

 tial basis of mineralogy as a true science. Another cause 

 may be traced to the different appearances, which the same 



