Maryland Gkoi.ociical Slkvey 577 



deeper than usual suggestive of C. cdiilnicta, occurs associated with the 

 preceding. It differs from C. conlnulu in the frequent presence of -i or 5 

 plications in sinus while length and ^\•idth are subequal in many indi- 

 viduals. Many specimens are quite convex. 

 Collection. — Maryland Geological Survey. 



CAilAROTCECHIA COXTRACTA (Hall) 



Plate LIU, Figs. 18-21 



Atrypa contracta Hall, 1843, Geol. of N. Y.; Rept. on the 4th Dist., pi. Ixvl, 



fig. 3. 

 Khynchonella (Ste.nocisma) cont)-acta Hall, 18GT, Pal. of N. Y., vol. Iv, p. 



351, pi. Iv, figs. 26-39. 

 Camarotocchia contracta Hall and Clarke, 1894, Pal. of N. Y., vol viii, pt. ii, 



pl. Ivii, figs. 28-32. 

 Camarotachia contracta Grabau and Shimer, 1909, N. Amer. Index Foss., vol. 



i, p. 288, figs. 352d-sf. 



Dcacriiytion. — Camarotoecltia contracta is a transversely oval shell with 

 fold and sinus clearly developed from the beak outMard and becoming 

 very conspicuous on the margin. The valves are relatively shallow and 

 the plications coarse. Of the latter the fold and sinus bear three or four 

 and each lateral slope 7-8. 'J'he boundary plications on fold and sinus 

 have specially broad inner slopes. 



Concerning the limits of this species see remarks under C. congregata 

 var. parJcheadeims. Typical C. contracta is characterized by its transverse 

 form, flat valves, deep sinus and angular plications, 3 of which occupy 

 the sinus. It occurs chiefly in the upper strata of the Chemung. 



.Length 15 mm.; width 18 mm. 



Occurrence. — Jennings Formation, Ghemung Member. Allegany 

 Grove, 29G0. ^ilSO: Xational Eoad, on Polish Mountain, 2929; Millstone, 

 3116 (small var.) ; 5 miles west of Piney Grove in olive shales. Specimens 

 from Millstone at 3116 are much smaller than tlie other forms termed 

 C. controfta. They also differ from the typical form in that tlie sintts 

 does not begin so near the umlin and is not so pronounced, the umbo of 

 the ventral valves is unusually convex, the dental lamelliT? all longer. The 

 37 



