MUSEUM OF COMPARATIVE ZOOLOGY. 37 



Triodopsis Sanburni.^ 



Plate I. Fig. 9; Plate III. Fig. 3. 



Shell narrowly umbilicated, globose, depressed, thiu, sparsely hirsute, with 

 distant, scarcely perceptible wrinkles of growth, yellowish horn-colored ; whorls 

 five and one half, slightly convex, the last hardly descending, beneath convex ; 

 aperture oblique, lunate, trilobed, with a heavy, prominent, blunt parietal tooth ; 

 peristome white, broad, reflected, almost covering the umbilicus, thickened, 

 bearing on its right margin a large squarely truncated denticle, on its basil 

 margin a stout, bluntly pointed denticle, the two denticles separated by a small, 

 rounded sinus. Greater diameter, 11 mm. ; lesser, 10 mm. ; height, 5 mm. 



Kingston, Northern Idaho (J. Rand Sanburn). 



Lingual membrane as usual in the genus. Teeth 26-1-26, with about eight 

 laterals on either side, the ninth tooth having its cutting point split, tlir eleventh 

 in another membrane : centrals with slightly developed side cusps and decided 

 cutting points : laterals like the centrals, but bicuspid : marginals long, low, 

 with two very wide, blunt cusps, the inner much the larger, both bearing long. 

 oblique, irregularly bind or trifid cutting points. (PL III. Fig. 3.) 



Genital system with no accessory organs. Penis sac long, cylindrical, some- 

 what attenuated at its apex, where it receives the vas deferens and retractor 

 muscle : genital bladder long, narrow, suboval : duct to genital bladder stout 

 below, gradually tapering above. The same arrangement is found in the geni- 

 talia of the typical devius. 



This shell, found in quantities living by Mr. Sanburn, shows no variation 

 excepting slightly in size. There are no individuals showing a transition to 

 forms of Mullani. It is nearly allied to that species as described by Mr. Bland. 

 It is, however, much less globose, and has its aperture very much more con- 

 tracted by teeth. The parietal tooth is not long and curving, but erect and of 

 equal width to its bluntly truncated top. The upper tooth on the peristome, 

 opposite, not above, the parietal tooth, is also erect and bluntly truncated. The 

 lower peristome tooth is bluntly triangular. The sinus between the two pa- 

 rietal teeth is small and rounded. 



I have described the shell as hirsute, though no hairs were found on the scars 

 which surely bore them. 



The general appearance of the shell is that of T. Hopctonensis. 



Triodopsis Harfordiana. 



Plate I. Figs. 6, 7. 



Shell umbilicated, depressed, thin, shining, sparsely hirsute, greenish horn- 

 colored, wrinkles of growth not prominent; whorls four and a half, hardly 

 convex, the last scarcely descending, deeply grooved behind the peristome, 

 hardly convex beneath ; aperture very oblique, lunate, trilobed, with a small 



