228 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



Fig. 498 of p. 279, Land and Fresh-Water Shells N. A., I, gives the 

 general arrangement of the teeth upon the lingual membrane. It is drawn 

 from the true northern A. Columbianus. Its general arrangement is as in 

 Patula. On PI. V. Fig. E, I have given more detailed figures of the denti- 

 tion of a specimen of this species. It will be seen that the central teeth have 

 a base of attachment longer than wide, with expanded lower angles and in- 

 curved lower margin ; the upper margin is reflected ; the reflection is large, 

 broad, and has a short, stout median cusp, bearing a long, stout cutting point ; 

 the side cusps of the reflection are subobsolete, but there are well-developed 

 triangular cutting points. The laterals are like the centrals, but asymmet- 

 rical by the suppression of the inner lower lateral expansion to the base of 

 attachment, and the inner side cutting point, the inner side cusps being still 

 subobsolete. The change from lateral to marginal teeth is shown in b and c, 

 the inner cusps and cutting point being greatly developed, and the base of at- 

 tachment is still narrower than in the first laterals. The marginals are shown 

 in d and e. They are about as high as wide, the reflection equals the base of 

 attachment and bears an extremely long, blunt, stout, oblique cutting point, 

 with a side spur upon the last, in the extreme marginals developed into a short, 

 stout, side cutting point. The cutting point of the marginalsjby its great devel- 

 opment forms the chief characteristic of the membrane ; it is well shown in 

 profile. 1 There were 22 perfect laterals in this specimen. The figure referred 

 to above shows only 12 laterals, with 113 rows of 56 1 56 teeth each. 



I have examined one specimen of A riolimax niger, J. G. Cooper, preserved in 

 spirit, belonging to the State collection of California, labelled and presented by 

 Dr. Cooper, and in all respects an authentic type. Agreeing with this type I 

 have other specimens from various Californian localities, so that I believe the 

 species to be well established and generally distributed along the coast of 

 California. 



From the Museum of Comparative Zoology at Cambridge, Mr. Anthony has 

 sent me a specimen, long preserved in alcohol, marked from San Mateo, Cali- 

 fornia. For reasons given below, I am inclined to consider this the form 

 described by Dr. Cooper as A, Californicus. I have had the opportunity of 

 examining another specimen of this form, received from Mr. Stearns, who col- 

 lected it near San Francisco. And recently I have examined specimens re- 

 ceived from Dr. Cooper. 



From Mr. Henry Hemphill I have received a specimen from San Mateo 

 County, California, which presents most decided specific differences from the 

 last-mentioned form, especially in its genitalia. Having considered the last- 

 mentioned form as A. Californicus, I was forced to consider this as A. Colum- 

 bianus, the only remaining described species. I had not at that time compared 



1 In only one instance have I seen marginal teeth as in my figure (of PI. V. Fig. F, d). 

 In all other specimens examined the marginals are as figured in PI. V. Fig. E, e, with one 

 long cusp and one obsolete side cusp. 



