476 On Succinea amphibia. 



of vitality as easily as the most puny. Concerning the me- 

 dullary substance Cuvier says, — " it possesses that most won- 

 derful of all properties, the power of transmitting to the mind 

 the impressions made on the external organs of sense, and 

 rendering the muscles subservient to the will. The brain 

 and spinal marrow are almost entirely composed of medullary 

 substance, and the nerves which are distributed through all 

 the organs capable of sensation, are in respect of their com- 

 position nothing but bundles or fasciculi of it." In the liv- 

 ing or recently destroyed insect, this substance is white and 

 pulpy, but in that which has become dry, it appears as minute 

 yellowish granules, — (g). 



At the base of the auricula, (antenna), as mentioned before, 

 is the loba, to the front of which is found the meatus, ( h, k, 

 I), that conveys sound to the tympanum, (n). At the base 

 is a bony operculum, in the shape of a shield, concave, and 

 furnished with muscles, by which the animal may close the 

 orifice at pleasure, (m). On the side of the tube nearest the 

 cranium is a channel for the passage of the muscles, {I). — 

 At the end of the meatus interims is situated the tympanum, 

 beyond it the labyrinth. 



My intention, as regards this matter, is to proceed with an 

 examination of one or more species in each order, and then 

 institute an enquiry into their comparative form, with the adap- 

 tation of the auricles to the habits of the creatures possessing 

 them. 



Birmingham, July 16th, 1838. 



Art. IV. On Succinea amphibia, (Drap.), and its varieties. By 

 Daniel Cooper, Esq. A.L.S., Curator to the Botanical Society of 

 London.* 

 The following short communication has been drawn up for 

 the purpose of pointing out some long prevailing errors re- 

 specting this mollusc, which, in marshy situations, is perhaps 

 the most common species in the neighbourhood of London, 

 and probably throughout the whole kingdom. 



MOLLUSC A, (Cuv.). 



First Section.— M OL LUSCA CEPHALA, (Ferrussac). 



Class. — Gasteropoda, (Cuv.). 



Order. — Pulmonifera, (Fleming). 



Family. — Helicidce, (Jeffrys). 



*Read before the Linnean Society of London, Deer. 19th, 1837. 



