138 PROCEEDINGS OF THE ACADEMY OF [1889. 



are well developed, they are singularly pale in color, and have a 

 more delicate structure than any of the species heretofore observed. 



They are also ornamented with small chocolate-colored spots or 

 mottlings, quite unusual to the species. Though secured in one lot, 

 their habitat is still conjectural. 



Reference was also made to a new species of Helix, found in the 

 Island of Xew Guinea. 



This the speaker had named Helix Dentoni in honor of the dis- 

 coverer, Mr. Wm, Denton, who died while pursuing his researches 

 in the wilds of the island mentioned. The type, which has been pre- 

 sented to the Academy, was received from Mr. Geo. W. Dean, of 

 Kent, Ohio, to whom it was sent from New Guinea by the sons of 

 Mr. Denton. Its habitat is therefore established. 



The species belongs to the sub-genus Trachia, its nearest ally being 

 H Tuckeri, Pfr. ; but it may readily be distinguished from the latter 

 by the continuous peristome, more oblique aperture and deeper con- 

 striction of the whorl behind the lip. 



In reference to the lasting character of the colors of shells when 

 properly cared for, attention was called to a magnificent Triton 

 tritonis belonging to the speaker. This specimen is 18 inches long, 

 11 inches high, and has an expanse of lip 6 by 9 inches. Though 

 known to have been out of its native element for more than fifty 

 years, the external colors are still perfectly patterned and brilliant, 

 while the crimson and white sun-burst covering the inside of the lip 

 is a bit of coloring which an artist might envy. 



May 21. 

 The President, Dr. Joseph Leidy, in the chair. 

 Twenty-eight persons present. 



In connection with the proceedings of the Biological and Micro- 

 scopical Section the following communication was made : — 



On the fore and aft poles, the axial differentiation and a possible 

 anterior sensory apparatus of Volvox minor. — Prof. J. A. Ryder 

 remarked that he had recently had an opportunity to study a very 

 large colony of Volvox minor Stein, which appeared in the aquarium 

 jars kept in the Conservatory of the Biological Department of the 

 University of Pennsylvania. As some of the singular features of 

 these alga? which he had noticed were apparently unrecorded, it 

 was desirable that they should be described in order that others 

 should have an opportunity to more fully investigate the facts and 

 their bearings upon the life-history of these singular organisms. 



It was noticed that there was an empty pole in every colony or 

 csenobium. This empty or non-spore-bearing pole was always the 

 anterior one, or that which was directed forwards in the act of 

 locomotion, which is effected by a rotating motion of the whole 



