MR. LOYELL EEEYE ON TESTACELLA. 



153 



On the Structure of the Mantle iu TestaceUa. 

 By Loyell Beeye, Esq., F.L.S. 

 [Read April 17, 1862.] 

 Among- some unpublished drawings of British niollusks obligingly 

 placed at niy disposal by the BeY. M. J. Berkeley, E.L.S., I haYe 

 been interested in finding a figure of TestaceUa Maagei with a dif- 

 ferent condition of the posterior extremity of the animal to that 

 represented in any preYious figure or description. Either the 

 mantle is produced externally on each side for the lateral embrace 



of the shell, or a pair of lobes is developed for that portion in con- 

 nexion with the integuments. Mr. Berkeley informs me that his 

 drawing was made from a living specimen given to him by 

 Mr. Sowerby about the year 1829, captured, he believes, in a 

 garden at Lambeth. " I am certain," he adds, " that it is correct ; 

 but unfortunately I can find no description." 



TestaceUa is a form of much importance in the molluscan series, 

 as being the only example of a Slug in which the pulmonary sac is 

 situated at the posterior extremity of the animal ; and it is the only 

 one of strictly carnivorous habits, burrowing into the ground to a 

 depth of two feet and more, and gorging voraciously upon earth- 

 worms more than equal to itself in size. The shell, covering the 

 pulmonary sac, is the first in the testaceous kingdom to be secreted 

 externally, and the first in which an indication is presented of the 

 spiral plan of growth which is gradually developed in the shell of 

 Daudebardia and Yitrina, and matured in the whorled Helix. 



Though unknown to Linnaeus, TestaceUa was discovered and 

 singularly well observed long before the publication of the 12th 

 edition of the ' SYstema Naturae.' In the Memoires de l'Academie 

 des Sciences of Paris for 1740 is a letter addressed to M. de Beau- 

 mur by M. Dugue of Dieppe, from which the following is an 

 extract. It has been alreadv cited by De Ferussac in his 

 1 Histoire des Mollusques ' (1819), vol. i. p. 89 ; but it is necessarv 

 here to repeat it. 



LINN. PROC. — ZOOLOGY, VOL. VI. 11 



