MUSEUM OF COMPARATIVE ZOOLOGY. 197 



Vertigo Oscariana, Sterki. 



This is the most peculiar of our species. It is of the size of milium, but oblong, 

 with either end nearly equally pointed, the last whorl being considerably narrowed 

 and flattened towards the subtriangular, small aperture ; shell thin, delicate, of 

 pale horn-color, as is the palatal wall and margin ; the latter simple and straight, 

 with a very slight, thin callus inside ; lamellce 3, whitish, rather small ; one aper- 

 tural, one columellar (longitudinal), and the inferior palatal ; some- 

 times tliere is also a very small superior palatal. Length 1.5, diameter 

 0.8 mm. 



This remarkable Vertigo has been detected in Eastern Florida, on the 

 coast at Mosquito Island, etc., by Mr. Oscar B. Webster and his father, 

 Mr. Geo. W. Webster, of Lake Helen, Florida. These gentlemen took 

 much pains to ascertain the range of distribution of this form and some 

 others, and it is consequently only just to name the species in honor of 

 Mr. Webster. The most striking character of it, besides the narrowed 

 last whorl, is the thin and straight palatal wall and margin, so tliat, indeed, the 

 shell appears to be immature. But when seen under a glass of suflBcient power, 

 the margin is completed, and, as already mentioned, there is a thin callus at a 

 little distance from the margin. Moreover, Mr. Webster wrote me that, of more 

 than 150 examples he had seen, all were alike. 



A few days ago, in a lot of P. corticaria, Say, from Ithaca, N. Y., sent from 

 Texas, there was one example of this species, the shell dead, but in fair condition, 

 a little larger and less fragile than the Florida examples, and with a well marked 

 callus corresponding to a slight but distinct crest. The specimen may have been 

 collected in New York, and from its appearance at least I would ascribe to it an 

 origin north of Florida. Since the above was written, I have found a few exam- 

 ples in drift from Guadalupe River, Texas, collected by Mr. J. A. Singley, sent by 

 Mr. Wm. A. Marsh. 



By the kindess of Mr. Webster I was enabled to see a living example. The foot 

 and the lower parts of the head are nearly colorless ; head, eye-tentacles, and neck 

 light gray. Jaw very tender, thin, pale yellow, consisting of about 14 longitudinal 

 plates, shorter and wider in the middle, longer and narrower toward either end ; it 

 is much like that of V. tridentata, Wolf. Odontophore about 0.36 mm. long, 0.1 mm. 

 wide, about 110 square rows in each f + t + I teeth ; central very small ; laterals 

 gradually passing into marginals; the latter serrate. Different from that of 

 V. tridentata. 



In drift with numerous minute shells, from Guadalupe River, Texas, kindly sent 

 by Wm. A. Marsh, I found one specimen of this species, which consequently is not 

 confined to Eastern Florida, where it was detected by Messrs. Webster, but may be 

 widely spread over the southern part of our country. 



Vertigo Oscariana, Sterki, Proc. Ac. Nat. Sci. Phila., 1890, p. 33 ; The Nautilus, 

 1890, p. 136. 



The above is Sterki's description, and the figure is drawn by him from the 

 type. 



