264 CAMBRIAN BRACHIOPODA. 



336p [U. S. National Museum]. (For stratigraphio position and association, see p. 143.) Upper Cambrian: Ungu- 

 lite grit, Kunitz, Government of Pskow, Russia. 

 Obolus (Schmidtia) celatus. I Helmersenia ladogensis. 



Obolus sp. - 1 Keyserlingia buchi. 



336q [Jeremejew, 1856, pp. 73 and 80]. (For stratigraphic position and association, seep. 143.) Upper Cambrian: 

 Ungulite sandstone near Ladoga, Government of St. Petersbm-g, Russia. 

 *Helmersenia ladogensis. 



336r [Mickwitz, 1896, p. 137]. (For stratigraphic position and association, see p. 143.) Upper Cambrian: Obolus 

 sandstone in the entire region between the Volkhof (Wolchow) and Sjass (Sias) rivers on the east and 

 Baltischport on the west, governments of Novgorod, St. Petersburg, and Esthonia, Russia. 

 Obolus apollinis. 



336s (references follow species). (For stratigraphic position and association, seep. 143.) Upper Cambrian: Obolus 

 sandstone at Narwa, Government of Esthonia, Russia. 

 Obolus apollinis (U. S. National Museum). 

 Obolus apollinis ingricus [Eichwald, 1843, p. 146]. 



336t [Eichwald, 1843, p. 146]. (For stratigraphic position and association, see p. 143.) Upper Cambrian: Obolus 

 sandstone at Wiems, 5 miles (8 km,) north-northeast of Reval, Government of Esthonia, Russia. 

 Obolus apollinis. 

 Obolus apollinis ingricus. 



336u [Eichwald, 1860, p. 925]. (For stratigraphic position and association, see p. 143.) Upper Cambrian: Obolus 

 sandstone on the bank of Louga (Luga) River, southwest of St. Petersburg, Russia. 

 Obolus apollinis. 



336v [Gagel, 1890, desc. of PI. I]. (For stratigraphic position and association, see p. 143.) Ordovician: Echino- 

 sphxrites limestone at Reval, Government of Esthonia, Russia. 

 Siphonotreta unguiculata. 



336w (references follow species). (For stratigraphic position and association, see p. 143.) Ordovician: Near Paw- 

 lowsk, near St. Petersburg, Russia. 

 Siphonotreta unguiculata [Eichwald, 1840, p. 140 (26)]. 

 Siphonotreta verrucosa [Eichwald, 1840, p. 141 (27)]. 



336x [de Verneuil, 1845, p. 287]. (For stratigraphic position and association, see p. 143.) Ordovician: In the 

 Archangel quarry, on Volkhof (Wolchow) River, east of St. Petersburg, Russia. 

 Siphonotreta unguiculata. 



336y [U. S. National Museum]. (For stratigraphic position and association, see p. 143.) Passage beds between the 

 Upper Cambrian and the Ordovician: Glauconite limestone at Popowka, near St. Petersburg, Russia. 

 Siphonotreta unguiculata. 

 Siphonotreta verrucosa. 



336z [Schmidt, 1861, pp. 218 and 248]. (For stratigraphic position and association, see p. 143.) Passage beds 

 between the Upper Cambrian and the Ordovician: Orthoceratite limestone ("Vaginatenkalk") at Narwa, 

 Government of Esthonia, Russia. 

 Siphonotreta unguiculata. 



337 [Schmidt, 1861, pp. 218 and 248]. (For stratigraphic position and association, see p. 143.) Passage beds 

 between the Upper Cambrian and the Ordovician: Orthoceratite limestone ("Vaginatenkalk") at Erras, 

 85 miles (137 km.) east of Reval, Government of Esthonia, Russia. 

 Siphonotreta unguiculata. 



337a [Schmidt, 1861, pp. 218 and 248]. (For stratigraphic position and association, see p. 143.) Passage beds 

 between the Upper Cambrian and the Ordovician: Orthoceratite limestone ("Vaginatenkalk") at Kusal, 

 25 miles (40 km.) east of Reval, Government of Esthonia, Russia. 

 Siphonotreta unguiculata. 



337b [Schmidt, 1861, pp. 218 and 248], (For stratigraphic position and association, see p. 143.) Passage beds 

 between the Upper Cambrian and the Ordovician: Orthoceratite limestone ("Vaginatenkalk") at Reval, 

 Government of Esthonia, Russia. 

 *Siphonotreta unguiculata.'* 



337c [Schmidt, 1861, pp. 218 and 248]. (For stratigraphic position and association, see p. 143.) Passage beds 

 between the Upper Cambrian and the Ordovician: Orthoceratite limestone ("Vaginatenkalk") on Odens- 

 holm Island, 55 miles (88.6 km.) west of Reval, Government of Esthonia, Russia. 

 Siphonotreta unguiculata. 



a May be the type locality. Eichwald [1829, p. 274) gives it as " limestone at Reval." 



