28 BRITISH MOLLUSKS. 



In the year 1740, M. Dugue, a gentleman residing at Dieppe, com- 

 municated to the Academy of Sciences of Paris, the following interest- 

 ing discovery of the mollusk which has received the name of Testa- 

 cella : — "There is in this city a garden in which a slug has been found 

 that is unknown to the gardeners of the country. It is from eighteen 

 to twenty lines long, and is somewhat of the form of the red slugs 

 which crawl upon the earth and have no shell. It burrows in the 

 soil bike the earthworm, and goes out only at night. It carries 

 upon its tail a shell like a nail at the end of the finger, and is as 

 hard. The entire animal is so hard that one can scarcely cut it with 

 a knife. It has been kept in a pot with some earthworms three or 

 four inches in length and as stout as a pen ; it feeds on them though 

 much less strong in appearance. It occupied from four to five 

 hours in swallowing one entirely, but did not risk during this long 

 time losing its prey ; when once it has seized a worm by one end, 

 there is no chance of escape. It deposits its eggs in the ground per- 

 fectly round at first, and nothing more than a little pellicrde filled 

 with a viscous humour, but at the end of fifteen days, or a little more, 

 the humour thickens, the round form changes to an oval, and the 

 slug hatches it like a chicken." 



Linnaeus had not yet matured his system of nomenclature, and it 

 was not until sixty years later, that the Testacella was named by 

 Cuvier from specimens collected by M. Faure Biguet, at Crest in 

 the department of Drome. Subsequently it has been collected in 

 the centre and South of England and Ireland, in the Channel Islands, 

 in Spain, Portugal, Syria, Algeria, the Canary Islands, and the 

 West Indies ; and it has been abundantly bred at Bordeaux for ex- 

 perimental purposes, by M. Gassies, who in conjunction with M. 

 Fischer, has published a very admirable monograph of the genus. 



The interest attaching to Testacella in a systematic point of view, 

 arises from the circumstance of its being an intermediate link 

 between the two families of Limacinea and Colimacea. The pul- 

 monary sac which in Limax is in the front part of the body, and in 

 Parmacella, a genus inhabiting the South of France, is in the middle, 

 is in Testacella situated at the hinder extremity ; and in place of an 

 integumentary shield it is provided with a delicate mantle secret- 

 ing an external ear-shaped shell. The shell is composed of regular 

 concentric layers, commencing from a subspiral umbonal nucleus, 

 and presents the first indication of the convoluted plan of growth, 

 which is developed in Vitrina and Helix, and becomes the typical 

 structure of the class. But Testacella possesses essential characters 



