BRACK IO POD A. 345 



Llngula clatlirata.] 



with exceedingly little convexity, appearing in most cases, perfectly flat. Anterior 

 third or half usually uniformly rounded. Front margin occasionally somewhat 

 straightened. Sides gently convex to near the beak which, in none of the numerous 

 specimens examined, seems ever to have formed an acute termination. Surface with 

 only very faint concentric undulations; even these are quite obsolete, when the shell 

 is preserved in a shaly or impure limestone matrix." 



Formation and locality. Puttier rare near the base of the Hudson River group near Granger and 

 Wykoff, Minnesota. It also occurs at Graf, Iowa, and Cincinnati, Ohio. Also in the middle and upper 

 portion of the Trenton at Frankfort and Paris, Kentucky. 



Collectors. E. O. Ulrich and C. Schuchert. 



LINGULA CLATHRATA, n. sp. 



PLATE XXIX, FIGS. 42. 



This little Lingula is, in form and convexity of valves, much like L. riciniformis 

 Hall, except that it is somewhat wider posteriori} 7 . Like that species, this one also 

 shows plainly the Obolella stage of growth. It is, however, much smaller than that 

 species, besides differing from it and all associated species of Lingula in having from 

 twenty-two to twenty-eight wavy, imbricating, transverse lines crossing the marks 

 of growth and restricted to the external shell layer. These lines begin to appear 

 on the medial portion of the valves quite close to the apex, or during early nealogic 

 growth. They are closely arranged and gradually become more distant and extend 

 across the valve from side to side. Those which are continuous from one margin to 

 the other occupy but a small portion of the shell, becoming disunited medially at 

 about one-third the length of the valve from the apex and cease to be developed a 

 short distance beyond mid-length or may be continued to near the anterior margin. 



Interior characters not defined beyond a low median septum extending for two- 

 thirds of the length of the shell from the apex. 



Length and breadth of an ordinary specimen 4.5 mm. and 2.5 respectively. 



The transverse surface lines appear in a number of other forms occurring in 

 older and younger formations. The earliest species with it known to us is Lingulella 

 stoneana Whitfield* of the St. Croix formation. The next younger one is the species 

 here described followed by Lingula tceniola Hall and Clarkef of the New York Clinton. 

 The latter species possesses this feature very strongly developed, obscuring the con- 

 centric growth lines, and " are equally visible on the inner side of the shell, a character 

 not seen in the other forms. Of precisely the same character is the ornamentation 

 in L. zebra Barrande from the Bohemian Etage E.":}: L. spathata of the Lower 

 Helderberg also has these lines sharply developed and more closely arranged than 



Geol. Wisconsin, vol. iv, p. 3, pi. xxvil, figs. 6, 7; 1882. tPal. N. Y., vol. viii, pt. i, p. IS; 1892. *Ibid., p. 18. 



