NO.U83. UROCOPTJD MOLLUSKS—BARTSCH. 153 



teeth, pending from the parietal wall. These teeth are placed upon a 

 slender raised spiral thread, which disappear anteriorly and posteriorly 

 with the teeth. The teeth are not apparent in the aperature. The 

 internal septa are extremely thin and transparent. The tj'pe has 17 

 whorls (the nucleus and probably the first two of the succeeding- turns 

 being lost), and measures: Length, 11.5 nun. ; greatest diameter, 3.6 mm. 

 Two specimens and three fragments of this species, ('at. No. 188181 

 U.S.N.M., were collected by J. N. Rose and J. H. Painter at Tehu- 

 acan, Puebla, Mexico. The other specimen also has the nucleus and 

 a few more of the succeeding whorls, decollated. It has 13 whorls 

 remaining and measures: Length, 12.2 mm.' diameter, 3.6 mm. 



HENDERSONIELLA Dall. 



Shell discoid, with a single internal parietal lamina, the aperture 

 and part of the last whorl free from the disk and recurved so that the 

 holostomatous aperture lies above the disk and with the plane of its 

 margin nearly or quite parallel with the plane of the shell coil. Soft 

 parts resembling those of Holoiiplra. 



This genus is dedicated to John B. Henderson, jr., known in con- 

 nection with his studies of the Antillean land shells. It is an animal 

 of the Urocoptid group which has taken upon itself a discoid form, 

 something hitherto unknown in that assemlily and therefore of unusual 

 interest. 



HENDERSONIELLA PALMERI Dall. 



Ilendersonia palmeri Dall, Smith. Misc. Coll. (Quart. Issue), III, 1905, p. 187, 

 pi. XLiv = Henikrsoniellajmlmeri Dall, Idem, p. 239. 



Plate V, figs. 1-4. 



Shell thin, depressed, nearl}^ fiat above, with the periphery com- 

 pressed and keeled; the umbilicus wide, shallow, saucer like, its margin 

 subangular; the suture distinct, rather deep, not channelled but with 

 the whorls between distinctly rounded; nuclear whorl polished, rather 

 prominent, the eight subsequent whorls subequal, closely coiled; the 

 termination of the last whorl divergent, wholly free from the body, 

 curved upward with the aperture nearly or quite in the plane of the 

 surface of the spire, dilated and cup-like toward the aperture, the 

 peristome continuous, expanded, and slightly reflected, with an obscure 

 wave on the proximal side; surface striated with feeble lines of growth, 

 color about that of J*oIt/gf/ra microdonta Deshayes, a pale horn color 

 or ashy brown, whitish on the peristome; lumen of the whorls sub- 

 rectangular before becoming solute; about one-fourth of the last whorl 

 contains a single prominent, somewhat oblique elevated lamina on the 

 body side, which diminishes gradually toward each end, the distal end 

 becoming obsolete about the point where the last whorl leaves the coil 

 and begins to grow independently; the wave in the free portion seems 

 to be a reminiscence of the infold in ordinary IIoloKpirds^ but is almost 



