1896.] NATURAL SCIENCES OF PHILADELPHIA. 401 



The total, after suppressing a number of synonymous names, 

 amounts to twenty-seven discriminable forms collected from seven 

 out of the twelve principal islands by Dr. Baur. 



Dr. Baur's results leave little room for doubt that a thorough ex- 

 ploration of all the islands, and especially of Albemarle and Nar- 

 borough, would add materially to the number of determinable forms 

 and, therefore, that the time for finally discussing or speculating 

 upon the distribution of the species among the several islands has 

 not arrived. Albemarle, much the largest, should when explored 

 yield a larger harvest than the much smaller Charles or Chatham 

 Islands, which seem to have been better explored, because they have 

 better anchorages for a vessel. Narborough,said to be very fertile, 

 has not been explored at all for land shells; we have nothing at all 

 from Abingdon or Tower, and only three species from Bindloe. 



Nearly all the land shells of the Galapagos are more or less arbo- 

 real and pass much, if not the whole, of the dry season attached to 

 branches of shrubs or trees by a deposit of tough dry mucus form- 

 ing a hermetic seal to the aperture, as well as a means of fixation. 

 So tough is this material, that, when dry, the bark or the shell will 

 break easier than the epiphragm if one tries to dislodge a specimen. 

 The mucus is poured out in such quantity as not only to close the 

 aperture of the shell with a brownish parchment-like membrane, 

 but to fill the minor irregularities of the surface upon which the 

 aperture rests and to rise around the outer margin nearly a milli- 

 meter above the edge of the shell. About a third or half a turn 

 further inside the shell, the animal constructs a second epiphragm, 

 behind which it rests in a torpid state until a change in the season 

 leads to its awakening. Several specimens of Bulimulus planosjnra 

 which had been gathered more than a year and kept in a corked 

 vial, when they reached my hands, still contained the living animal 

 in his self constructed refuge, and doubtless other species would have 

 done the same if they had not been put in alcohol. Nearly all of 

 Dr. Baur's living Bulimuli were collected during the hibernating 

 season as indicated by the remains of bark and epiphragm still ad- 

 adhering to them. 



Of the species not known to construct an epiphragm there are 

 only a few identifie<l from the islands, three small forms of Helici- 

 dee, a Leptinaria and HeUclna, besides the semi-amphibious salt- 

 marsh loving Auriculldce, etc. The Helidna has a shelly operculum 

 with which it can hermetically seal its shell. Both it and the Hel- 



