stantow.] NERITIDiE. 129 



always lower than the middle portion of the dorsal region in front of it, 

 directed obliquely backward, and in well-preserved specimens minutely 

 subspiral at the immediate, more or less oblique apex; inner lip very 

 broad, or having the form of a thick, smooth, convex septum that ex- 

 tends forward more than half the length of the shell; outer lip thick- 

 ened, obtuse and smooth within ; open part of the aperture small and 

 transversely semicircular. Surface with moderately distinct lines of 

 growth. 



ls Length of one of the largest specimens found, 0.62 inch; breadth, 

 0.50 inch; height or convexity, 0.33 inch." 



The variety weberensis White, which was found in the same layer with 

 the typical form, was described as follows : 



" Shell small, depressed, almost regularly elliptical in outline, nearly 

 regularly convex above, and nearly flat or longitudinally slightly con- 

 cave beneath; beak very small, apparently making about one volution, 

 turned a little to the dextral side of the shell, resting upon the thick- 

 ened posterior margin, but not projecting beyond it, the posterior mar- 

 gin being slightly reflexed so as to obscure the incurved apex ; inner 

 lip broad, smooth, flat, or concave longitudinally, and slightly convex 

 laterally, apparently occupying more than half the under surface of the 

 shell ; outer lip moderately thin, smooth, or at least not crenulate. Sur- 

 face marked by ordinary lines and undulations of growth, and upon the 

 middle portion of the anterior half by five or six narrow, slightly raised, 

 obscure, radiating ribs, with spaces between them a little wider than the 

 ribs. In some cases there are also other obscure radiating lines upon 

 the anterior flanks of the* shell. 



"Length, ll mm ; breadth, 8 mm ; height, 5 m,n . Some examples in the 

 collection are larger, but none of them quite equal in size the larger 

 examples of the typical forms of the species. 



" This variety, although perhaps connecting the typical forms with 

 N. (V.) carditoides Meek, differs from it in the number and character of 

 its costte, the proportions of the shell, and its smaller size. At one 

 time I thought, as did also Mr. Meek, that this variety might prove to 

 be specifically distinct from the typical forms of 1ST. ( V.) patelliformis, 

 but study of collections since made at the typical locality shows that 

 intermediate forms exist, associated with this variety and the typical 

 forms in the same layer." 



It should be added that the inner lip of this species is slightly den- 

 ticulate on the margin. 



The name Velatella was proposed by Meek as a subgenus of Neritina 

 to include this and a few other Cretaceous species. It was adopted by 

 White, who gave a diagnosis of it in the Ann. Eept. U. S. Geol. Sur. of 

 the Territories for 1878, p. 27. It seems to me to be scarcely distinct 

 from JJostia, from which it differs "in its more nearly perfect bilateral 

 symmetry and its minute apex." 



Locality and position. — Abundant in certain layers near the base of 

 Bull. 106 9 



