SUBAI.PINE MOLLUSCA. 83 



Black River, Wash. Ter., but each shows slight differ- 

 ences, hardly specific. 



Fig. 26 has the sides less parallel, or straight, the pos- 

 terior slope flatter; fig. 27 is wider before apex as is fig. 

 28, but less oval, both approaching the outline of fig. 29, 

 but being much larger. 



The nearest approach to A. cauriiius seems to be in A. 

 ovalis Morse, from Maine, but that is less than half as 

 large, pale yellow and wider in front. (See Binney's L. 

 andF. W. Sh., II, 156.) 



A. FRAGiLis Tryon. In the synopsis in Vol. IV, I con- 

 side red yra^//?s a small variety of caurimis, having "apex 

 more posterior, lower, narrower, anteriorly wider," and 

 in those points the other three forms here figured are in- 

 deed intermediate. But in size they are like canriniis, 

 while the numerous specimens of fragilis since found in 

 various portions of California, below 500 feet elevation, 

 all have nearly the same size and form as the type. 

 Those figured show that its variations in width are great, 

 if the type is as narrow as stated by Tryon. I have, 

 however, never seen any like it in that respect, and Try- 

 on's remark that its "sides are nearly parallel, or slightly 

 incurved in the middle," show that one of its characters 

 most like caiirinus is not constant. The usual oval form, 

 more abrupt slope behind and small size, may be consid- 

 ered proofs of specific distinctness, until more connecting 

 links are discovered. Both fragilis. and caiiriuiis have 

 been called similar to A. parallelus Hald., but are quite 

 distinct, fragilis being much nearer to rividaris Say. 



Another peculiarity of this small species is its close 

 likeness in form to the first stage of growth in Gundlachia 

 californica, the two being found together, and are possi- 

 bly only one species at different ages. 



In Binney's work, p. 139, he mentions in a foot note, 



