I9 2 NEW YORK STATE MUSEUM 



Genus rhynchotreta Hall 



[Ety.: pijyxa?, beak; rpr/rd, with a hole] 



(1879. N. Y. state inns, nat. hist. 28th an. rep't, p. 166; 1893. 

 Pal. N. Y. v. 8, pt 2, p. 185) 



Shell triangular; surface with angular plications. Beak of pedicle 

 valve straight, produced beyond that of the opposite valve, extremity 

 perforate, the foramen with an elevated margin. Two longitudinally 

 striated deltidial plates fill the delthyrium. Teeth slender, curving, 

 proceeding from a broad curving hinge plate in the pedicle valve. 

 Brachidium a slightly modified loop. 



Rhynchotreta euneata var. americana Hall (Fig. 105). 



A try pa euneata Hall (1852. Pal. N. Y. 2:276, pi. 57, 



fig. 4a-r) 



Distinguishing characters. Triangu- 



lar and cuneiform outline; longer 

 \V> n ,,, than wide; elongate angular beak 



of pedicle valve with compressed, 

 flat or concave sides; wide, deep sinus 

 in adult, extending two thirds to the 

 beak; profound frontal emargination; 

 strong angular plications, three in 



Fig. 105 Rhynchotreta euneata var. 



americana sinus, four on fold, the two central ones 



most prominent; numerous regular, fine thread-like concentric 

 striae; minutely papillose surface. 



Found in the Clinton lenses and the lower Rochester shale and 

 particularly in the Bryozoa beds, where it is abundant; rarely above 

 this. Niagara sections. Also at Lockport and elsewhere (Hall). 



Genus camarotoechia Hall & Clarke 



[Ety.: y.ap.dpa, arched chamber; -oTxo$, partition] 



(1893. Pal. N. Y. v. 8, pt 2, p. 189) 



Shell rhynchonelloid, trihedral in contour, with shallow pedicle 

 and convex brachial valve; no hinge area; beak of pedicle valve 

 projecting and incurved. Surface radially plicate, sinus and fold in 

 pedicle and brachial valves respectively. Distinctive internal char- 

 acters (separating this genus from other " Rhynchonellas ") are: a 



