PLATE 7 



Figs. Pahlenella trigonula (Eichwald) 



1, 3. — Ventral and dorsal exteriors. Dorsal valve concave. 

 2. — Ventral interior, showing deltidium and sessile spon- 



dylium. 

 4. — Dorsal interior, showing short brachiophores, chi- 

 lidium, and elevated muscle area. 

 Ordovician (Canadian, Walchow, B2),Popovka, near 

 Leningrad, Russia. Cat. No. S 370. x 2. 



Aff. Vellamo multicosta (Hudson) 



5, 11. — Views of the same ventral interior, showing rem- 

 nant of imperforate deltidium. 

 8. — Ventral interior, showing septum dividing two closely 

 apposed pallial trunks, and, outside these, ovarian 

 areas as in Glyftorthis et al. 

 9. — Dorsal interior, showing cardinalia and musculature. 

 10. — Ventral interior, showing muscle impressions on spon- 

 dylium. 



These shells are doubtfully referred to Vellamo, 



differing from that genus in having what appears to 



be an imperforate deltidium, and in details of the 



dorsal valve. 



Ordovician (Chazy), Sloop Bay, Valcour Island, 



N. Y. Cat. No. S3 59. x 2. 



Vellamo trentonensis (Raymond) 

 H. — Ventral interior, showing spondylium and its support- 

 ing septum, and deltidium. 

 28. — View of interarea and deltidium. Note position of 

 teeth. 



Ordovician (Galena, bed 6), Kenyon, Minn. Cat. 

 No. S342. X 1.5. 



18. — Dorsal interior, showing anchor-shaped cardin.ilia and 

 musculature. 

 Ordovician (Galena), Cannon Falls, Minn. Cat. 

 No. 8 348. X 1.5. 



Cf. Vellamo squamata (Pahlen) 



1 5. — Interarea. 



31. — Interior, showing spondylium. 



Ordovician (Cj) , Kohtla, Estonia. Cat. No. S 2 1 5 . 



xl.S. 



Figs. Vellamo cf. emarginata (Pahlen) 



16, 29, 30, 32. — Posterior, ventral, lateral, and dorsal views 



of the same individual, showing details of ornamenta- 

 tion and contour and outline of valve. 

 Ordovician (Mohawkian, Wesenberg), Wesenberg 

 quarries, Estonia. Cat. No. S 339. x 1.5. 



Vellamo verneuili (Eichwald) 



24, 27. — Dorsal and ventral exteriors of type species of 

 genus. 

 Ordovician (Cincinnatian, Lyckholm, F^), Kertel, 

 Estonia. Cat. No. S 347. x 1.5. 



Vellamo diversa (Shaler) 

 25. — Dorsal interior, showing cardinalia and musculature. 

 Ordovician (Ellis Bay), Junction Cliff, Anticosti. 

 Cat. No. 10335 Y. P. M. x 1.5. 



Apomatella ingrica (Pahlen) 



6, 7.- — Views showing spondylium. 



12. — Ventral exterior, showing also dorsal valve in con- 

 junction. 

 13. — Ventral exterior, showing procline position of inter- 

 area. 



These shells may be somewhat remote from the true 

 Vellamo line. 

 Ordovician (Canadian, Walchow, B„), Popovka, 

 near Leningrad, Russia. Cat. No. S2104. x 2. 



Clitambonites adscendens (Pander) 



17, 19, 22, 23. — Posterior, dorsal, ventral, and lateral views 



of exterior. Note particularly ornamentation and 



procline interarea. Deltidium commonly imperforate 



in adult shells, x 1.5. 

 20, 21. — Ventral and dorsal interiors, the former showing 



the spondylium. Note peripheral border or frill. 



x 1.5. 

 26. — Enlargement of exterior of specimen in fig. 19, 



X ca. 4.5. 

 Ordovician (Canadian, Kunda), Popovka, near Len- 

 ingrad, Russia. Cat. No. S 372. 



208 



