THE NAUTILUS. 21 



in the same manner that adult Gillia and other Amnicolidae 

 browse over vegetation, the proboscis moving slowly about and 

 the radula being protruded as in the adult animal. There 

 appeared to be a regular circular movement of the embryo 

 around the area of the egg capsule. A favorite position of 

 the young animal when at rest is shown in figure 5. The 

 rostrum appears to be cleft at the extremity in some individ- 

 uals and the anterior part of the foot varies greatly in form 

 when the young animal is active (fig. 6). 



The embryonic shell is transparent, spermaceti-white in 

 color and about 1.25 mm. in diameter. It consists of rather 

 more than one whorl which enlarges rapidly (fig. 7). The 

 nucleus and a large part of the shell is covered with very fine 

 spiral lines, the lines of growth beginning abruptly near the 

 aperture. The umbilicus is of medium size and rather deep 

 (fig. 8). 



Amnicola oneida or bakeriana Pilsbry. PI. 2, figs. 9, 10. 



The lenticular eggs of Amnicola (figs. 9, 10) were notably 

 abundant in many localities covering all objects on the bot- 

 tom, including living and dead vegetation, dead and living 

 shells, and bottom debris. Two species, recently described, 1 

 are represented. It is impossible to differentiate the eggs of 

 the two species, as both occurred with the eggs, but it is sus- 

 pected that the narrower form of egg (fig. 9) is from oneida. 

 and the wider form from bakeriana. (fig. 10). It will be 

 noted that the form of these eggs differs from the figure given 

 by Stimpson - for Amnicola limosa in which the egg is much 

 attenuated at both ends. The eggs of the new Amnicola were 

 especially abundant in filamentous algae (Cladophora fracta 

 and (Edogonium species), the long filaments often being cov- 

 ered with the lens-shaped eggs. Scirpus, Vallisneria, and 

 other plants were also used for attachment. An effort was 

 made to ascertain the number of eggs on certain species of 

 plants in a measured area, with the result shown in table 

 No. 2. In Vallisneria, eggs occurred on both sides of the leaf. 



1 Pilsbry, NAUTILUS, XXX, pp. 44-46, 1917. 



2 Researches upon the Hydrobiinae, etc., Smith, Miss. Coll., fig. 7, 1865. 



