578 Systematic Paleontology — UrrER Deyoniax 



reference of the latter individuals to ('. coniracia is not assured as they 

 approach some varieties of C. congregata var. parl-headensis. 

 Collection. — Maryland Geological Survey. 



Camaeotcechia horsfordi (Hall) 

 Plate LIII, Figs. 22-25 



Rhynchonella horsfordi Hall, 1860. ISth Rept. N. Y. State Cab. Nat. Hist., 



p. 87. 

 Rhynchonella (Stenochisma) horsfordi Hall, 1SG7, Pal. of N. Y., vol. iv, 



p. 339, pi. liv, figs. 24-32. 

 Camarotfjcchia horsfordi Hall and Clarke, 1893, Pal. of N. Y., vol. viii, pt. 



ii, p. 192, pi. Ivii, figs. 7-9. 

 Camarotachia horsfordi Grabau and Shimer, 1909, N. Amer. Index Foss., 



vol. i, p. 287, figs. 354a, b. 



Description. — '' Shell, in full-grown specimens, transversely subellipti- 

 cal; rostral portion sometimes a little extended; front nearly straight 

 or broadly rounded; length and width aljout as five to six or seven. 

 Young shells ovoid subtrigonal. 



"Ventral valve moderately convex, tiattened and incurved in front: a 

 slightly depressed sinus, appearing about the middle of the length, which 

 is flat in the bottom and curving abruptly upward? in front: lieak moder- 

 ately extended, abruptly acute and usually but little incurved. 



"Dorsal valve very gibbous in old shells, sloping abruptly to the beak; 

 depressed-convex in young shells. Mesial elevation defined below the 

 middle of the length. 



" Surface marked by about fifteen or sixteen to twenty-four well- 

 deiined. angular plications, of which four to six or seven mark the medial 

 sinus and fold, which are deeply bifurcated in front. On the sides and 

 towards the cardino-lateral margins of the shell the plications are less 

 angular; concentrically marked by fine undulating stria^. which are seen 

 towards the front, but rarely on other parts of the shell." Hall, 1867. 



Length 15 mm.; width "^0 mm. 



Of rare occurrence in the Parkhead. 



Occurrence. — Jennings Formation, Parkhead Member. Two miles 

 west of Pawpaw, West A^irginia; Sideling Hill Creek 2i/o miles above 

 mouth. 



Collection. — Marvland Geolooical Survev. 



