llELDKlIliKlHi F()i;.\IA 1 ION IN MaijVLAM) 35 



Ouly one specimen has been found in Maryland in the Cash Valley 

 section associated with Dalmanella clarki. S. eriensis is very closely re- 

 lated to S. modestus and 8. pUcatus of Maryland. It may be distinguished 

 from the former by its larger size and plications, and from the latter which 

 it so closely resembles by its less incurved beak, greatest width near middle 

 of valve, acute cardinal angles of brachial valve. 



Ocmirrence. — Heldekberg Formation, Keyser Member. Cash Valley. 



Collection. — Maryland Geological Survey. 



Genus RETICULARIA McCoy 



Eeticularia BicosTATA (Vanuxem) 



Plate LXXII, Figs. S-10 



Orthis Mcostatus Vanuxem, 1842, Geol. N. Y., Third Dist, pp. 91-94. 

 Spirifer bicostatiis Hall, 1852, Nat. Hist. N. Y., Pal., vol. ii, p. 263, pi. liv. fig. 4. 

 Spirifera bicostata Hall, 1883, 2d Ann. Rept. N. Y. State Geol., pi. Ixi, fig. 7. 

 Spirifer Mcostatus Hall and Clarke, 1893, Pal. N. Y., vol. viii, pt. ii, pp. 19, 

 37, pi. xxxvi, fig. 7. 



Description. — " Somewhat ovate triangular, the dorsal valve gibbous, 

 with the beak extended and incurved over a short triangular area ; ventral 

 valve convex; surface marked by conspicuous concentric subimbricating 

 striffi ; dorsal valve with a distinct plication on each side of the sinus, and 

 toward the base are two other obscure plications on each side, presenting 

 three and sometimes four gentle undulations on the margin on each side of 

 the center; cardinal line shorter than the width of the shell, and the area 

 scarcely extending so far as the cardinal line; extremities distinctly 

 rounded." Hall, 1852. 



The forms found are all small. The ovate triangular outline, con- 

 spicuous concentric subimbricating stria;, and plications distinguish it 

 from Spirifer modestus. It differs from Spirifer crispus of the Xiagara 

 in its fewer and less marked plications. 



Length 13 mm. ; width 11: mm. 



Occurrence. — Helderberg Formation, Keyser Member. Koundtop.' 



Collection. — Maryland Geological Survey. 



* It is possible that this species is from the Tonoloway formation. 



