1 82 Bulletin 31 ,i8a 



Verticordia eocensis Langdon, PL 55, Figs. 13-16 



V. eocensis l-,a.n^A^on, Amer. Jour. Sci., voL 41, 1886, p. 208. PL 6, 



fig. 13, Ala. GeoL Surv. , BulL i.— Aldrich. 

 Not V. eocosnensis Cossmann, Notes CompL, 1893, p. 7, pL i, fig. 6 



from Jackson, Miss. 

 V. eocenensis Dall, />ar/f/7;2, Trans. Wag., Ill, 1903, p. 1510. 



Langdoii' s original description. — Shell rotund, beak recurved, ele- 

 vated and striate, substance of the shell rather thick, lunule obscure, one 

 prominent cardinal tooth, lateral teeth oblique, margin dentate and crenu- 

 lated between dentitions ; nacre brilliantly pearly ; muscuIar|impressions 

 two, profound ; pallial line obscure ; closel}' ribbed ; ribs about 16, crenu- 

 late, radiating regularly from the beak and slightly recurved. 



Length .25, Breadth .25, Height .06, 



This, I believe, is the first Verticordia described from the Eocene, 

 there having been only three species known among living and fossil shells, 

 two of these being Miocene. Differs from V. einntonsi Con., in being ro- 

 tund and having more ribs, and from V. cardiiforviis Wood in having no 

 striations between the ribs, in being more rotund, and showing no incurv- 

 ing of the ribs as they approach the ventral margin. 



Claiborne, Ala., and Jackson, Miss. 



In the typical form eocensis there is not much abrupt varia- 

 tion in the spacing or size of the ribs. However, a little irregu- 

 larity is noticeable in about the third or fourth from the posterior 

 margin. 



In our specimens from Hickory and the Sabine River, from 

 the St. Maurice horizon, the tendency to irregularity becomes 

 more noticeable. There are three posterior ribs, then a rather 

 broad space, then two ribs slightly closer together followed by 

 about eleven quite evenly spaced. 



In the form described by Aldrich as sotoensis (The Nautilus, 

 vol. 16, 1902, p. 100, pi. 4, figs. 19-21) there are two posterior 

 ribs, then a space, anterior to which there are twelve ribs (see 

 pi. 55, figs. 10-12). 



For the reader's convenience we here include Aldrich' s de- 

 scription of sotoensis : 



Shell small, strongly ribbed with twelve ribs, then a blank space, 

 then two ribs near the margin, beaks blunt and rounded, ventral margin 

 serrated ; internal tooth long and curved. Interior very porcellaneous ; 

 muscular scars slightly impressed. 



