Characters of the genus Pedipes. 297 



Testa soHda, ovalis, striis spiralibus sculpta, unicolor. Spira brevis. 

 Apertura ringens, superne integra. Epidermis nulla. 



Animal littorale, revera marinum, et branchiis spirans. 



The remarkable shape of the foot, inducing a corresponding pecu- 

 liarity in the mode of crawling, (well described by Adanson), is the sole 

 external character by which the animal of the present genus is distinguish- 

 able from Melampus. Yet this character, combined with those of the 

 shell, is surely enough to warrant their separation. I am indeed inclined 

 to believe, th?t the different modifications in shape of the foot, will, in 

 many cases, be found to afford valuable aid, to a more natural and 

 scientific arrangement of the marine Gasteropoda into genera, than the 

 present state of our knowledge permits. 



The genus Pedipes was founded long ago by Adanson ; and both its 

 animal and shell are admirably and correctly described by him. Yet 

 Bruguiere united it with his Bulimi ; and Lamarck has confounded it 

 with Tornatella. 



The species from which the above description and accompanying draw- 

 ings were made, I once considered distinct from Adanson's species : but a 

 careful comparison with his description (his figure is somewhat rude and 

 incorrect) has satisfied me of its identity ; the only dift'erence being in 

 the number of volutions, which in my specimens are 4 or 4| instead of 

 6, and in the aperture being tvdce as long, instead of " un peu plus 

 " long que le sommet." It occurs mixed with Melampus cequalis and 

 exiguus, but in far greater profusion, under stones upon the beach, on the 

 north side of Pta. Sao Laurengo ; the eastern point of Madeira. 



That it truly belongs to the Pectinibranchia has never been doubted, 

 and is indeed beyond all question. From a number of experiments, 

 conducted simultaneously, and with a similar view to those above recorded 

 of Melampus, upon specimens brought from the same spots and found 

 under the same stones with Melampodes, I shall only select the following. 



Experiment 14. 

 July 19. Two specimens of Pedipes afra inclosed in separate bags, 

 and each immersed in a glass of sea-water. 



20. Both alive and healthy. 



21. One quite lively, the other sickly and retracted. Water 



changed with both. 



