216 



Found in the Encrinal limestone, at Section 5; the Sticto- 

 pora and Demissa beds, at Section 5 (abundant) ; shales be- 

 low the Trilobite beds, in Avery's Ravine (rather common) ; 

 Pleurodictyum and Calcareous beds above (very rare). 



Spirifer (Martinia) subumbonus. Hall. (Fig. 124.) 

 ( Pal. X. V., Vol. IV.. p. 231, PI. XXXII.) 



DistinguishingCharacters. — Very small size (for a Spirifer) ; 



vmw '/p gibbous character; rounded 







c a r d i n a 1 extremities; 

 smooth or concentrically- 

 striated surface; highcardi- 



Fig. 124. Spirifer subumbonus. Dorsal and . ... . 



profile views of a specimen, enlarged; en- nal area 111 pedicle Valve, 



largement of the surface to show the pits 



(after Hail). with rounded margins; ab- 



ruptly incurved beak of pedicle valve; narrow, almost obso- 

 lete, and never pronounced, sinus; absence of fold, an im- 

 pressed line occasionally marking the center of the brachial 

 valve: in well-preserved and partly exfoliated specimens 

 numerous puiictse or pits appear, probably marking the 

 former position of spines. 



Found in the Styliolina band, at Section 1 ; Moscow 

 shale (upper four feet), at Sections 2, 8, 1 (rare); Hamilton 

 shales, about two feet below the Encrinal limestone, at Sec- 

 tion 6 (one specimen); also in the shale between the Nauti- 

 lus and Strophalosia beds, in Avery's Creek. 



Genus AMBOCCELIA. Hall. 



[Ety. : Ambon, umbo; koilos, belly.] 



(1860: I3tli Ami. Rep't N. Y. State Cab. Nat. Hist., p. 167. 

 1893: Pal. N. Y., Vol. VIII., Pt. II., p. 54.) 



Shell of small size; piano-, eoncavo-, or gently bi-convex, 

 the pedicle valve always deepest, and commonly extremely 

 convex, with a strongly marked, arched and incurved umbo. 

 A narrow median groove,more or less profound, is commonly 

 present. Thr cardinal area is arched, its margins are well 

 defined, and it is divided by an open delthyrium, with incom- 

 plete deltidial plates. Strong articulating teeth, and a- 



