I02 Bulletin 31 io« 



pi. 24, figs. 31-37 ; pi. 25, figs. 2-1 1. 



Conrad'' s original description. — Elongated ; umbonial slope angular 

 and obscurely plicated ; the posterior side produced, or rostrated with age, 

 and the extremity obliquel}' truncated ; beaks with concentric grooves ; in- 

 ner margin crenulated. 



Locality. — Claiborne, Ala. Middle Tertiary. 



This fine shell though variable in outline, is distinguished by a length 

 in proportion to its height, unusual in the geims, it is abundant, and a single 

 valve measures 2)4 inches in length and i inch and 3 tenths in height. 



Conrad gives a very good figure of an adult form of this 

 species in I S45 (Amer. Joi:r. Sci., vol. i, pi. ,2, labelled i by 

 mistake) and makes further descriptive remarks regarding the 

 3'oung on p. 396 of the same Journal, illustrating the same by 

 fig. 4, pi. 3. B}' mistake Conrad niuiibered a figure of alcefonnis 

 "2" on plate 3, which, according to the text, p. 403 should be 

 numbered "3". This slight error caused de Gregorio in his 

 famous Claiborne work to copy the figure and call it protexta (see 

 his pi. 25, fig. 12). Gregorio cites Conrad's work, giving the 

 page correctly, but gives the wrong year, i. e., 1833 instead of 

 1832. This oversight in dates probably caused him to wonder so 

 much why Lea did not cite the species at all though he (Greg- 

 orio) found it so abundantl3^ 



In the ver}^ earliest stage of growth this species shows a 

 more or less circular form, with concentric undulations corres- 

 ponding to those already described under clarkensis. But verj^ 

 .soon these broader undulatians give place to strong concentric 

 lines that are usually carried over to one-third the distance from 

 beak to base. This is the ver}^ same tj^pe of ornamentation seen 

 on var. ludovicianus just referred to but less extensive. In well- 

 developed protexhis the ligamental margin appears slightly more 

 concave than in clarkensis, the posterior is broader and the slight 

 depression below the umbonal ridge is not so conspicuous, but 

 the swelling jtist below or anterior to this furrow is much more 

 pronounced in protextiis. The slight concavity of the ligamental 

 margin has a tendenc}^ to give the beak an opisthogj^rate aspect. 

 Although there is considerable range in the extent of concentric 

 ornamentation in this species in adult shells no clear-cut varieties 

 based on this feature seem to be difFerentiable. The general out- 



