1901.] NATURAL SCIENCES OP PHILADELPHIA. 630 



palatal armature of short palatal plica?, precisely similar to the 

 structure still extant in certain other groups, Meg atop hcedusa for 

 instance. This became modified in two modes: (1) The interme- 

 diate plicai degenerated, resulting in such forms as typical C. 

 japonica, in which only the upper and lower plica? remain, or (2) 

 the intermediate plica? coalesced to form a lunella. 



That the loss of an even series of plica? has been a very recent 

 one in Stereop hcedusa is indicated by several facts. In species 

 which normally have but two palatal plica? sometimes individuals 

 or races occur in which small intermediate plica? are developed ; 2 

 and in species with a lunella, the earlier structure of a row of 

 plica? is perfectly developed in the stage of growth immediately 

 preceding the adult stage. 



Incidentally I may observe that the perplexing structural varia- 

 tion I formerly recorded in describing C. hondana is at least par- 

 tially explained by what I find to occur in the Stereophcediisce of 

 Kiushiu and Tane-ga-shima. I was dealing with a small series of 

 shells, part of which were not absolutely mature. 

 Clausilia brevior v. Martens. PI. XXXVIII, figs. 47, 48, 49, 50, 51. 



Von Martens. Sitzungsberichte der Ges. Naturforsch. Freunde in Ber- 

 lin, 1877, p. 109. Kobelt, Fauna Moll. Extramar. Jap., p. 78, PL 9, 

 fig. 4 (bad). 



0. tetraptyx v. Mollendorff, Journ. Asiatic Soc. Beng., LI, p. 7, PI, 1, fig. 

 7 (1882); 1885, p. 61. 



This species is not recognizably figured in Kobell's work. For 

 the purpose of more exact comparison with C. Addisoni, a fuller 

 account of the species than has been published is given below. 



The shell is thin, obesely fusiform, much attenuated and con- 

 cave-sided near the apex, the last three whorls inflated, the last 

 half of the last whorl more or less compressed, often conspicuously 

 narrower than the preceding whorl, as in the " nipponensis" form 

 of C. japonica. Pale yellowish brown; sharply, . very obliquely 

 striate or rib-striate. Whorls about 9^, the apex minute, but the 

 following whorl disproportionately large; next few whorls very 

 slowly increasing. Aperture squarish-ovate, the peristome ex- 

 panded, somewhat reflexed, thickened and white, hardly free 

 above, the upper margin parallel to the sutures. Superior lamella 

 thin and high, marginal, continuous with the spiral lamella which 



2 The evidence of this will be presented in a future paper dealing with the- 

 G. japonica group of Stereopficedusa. 



