PLATE 15 



Figs. Syntrophina campbelli (Walcott) 



1. — Ventral internal mold, showing impression of spon- 

 dylium. 

 2, 19. — Dorsal interiors, showing subparallel or divergent 

 brachiophore plates. Fig. 19 also shows impression 

 of small callosity at back of notothyrial cavity. 

 Ordovician (Canadian, lower Roubidoux), hill op- 

 posite McCabe, Missouri. Cat. No. S 1553. x2.65. 



Syntrophina breviseptata Ulrich MS. 

 15, 16. — Ventral interiors, 15 being an internal mold and 

 16 an impression taken from it. Spondylium well 

 shown. 

 17, 18. — Dorsal interiors, the latter an internal mold and 

 the former an impression taken from it, showing 

 divergent brachiophore plates. 

 Ozarkian? , Phillipsburg, Quebec. Cat. No. S 1 5 5 1 . 

 x2. 



Syntrophina palmata (Cleland) 



30, 31. — Dorsal internal mold and impression taken from it. 

 The latter shows the adductor impressions and the 

 posterior callosity. 



Ordovician (Canadian, Tribes Hill), Fort Hunter, 



N. Y. Cat. No. S 1544. x2.65. 



Syntrophia cf. lateralis (Whitfield) 



3. — Replica of dorsal interior, from original in Ulrich 

 Coll., U. S. Nat. Mus. Shows narrow, short cru- 

 ralium, which resembles that of some rhynchonelloids. 



Ozarkian ? (Bg), Phillipsburg, Quebec. Cat. No. 



S1574. x2. 



Syntrophia lateralis (Whitfield) 



27, 28. — Lateral and front views of ventral interior, the 

 latter showing musculature. 



29, 32. — Posterior and dorsal views of complete individual. 

 From Walcott, Camb. Brach., pi. 102, figs. 6e-g, 

 after Hall and Clarke, Pal. N. Y., vol. 8, pt. 2, 

 pi. 62, fig. 9. 



Syntrophinella typica Ulrich MS. 



4, 5. — Ventral and dorsal exteriors, showing faint radial 

 sculpture. 



13. — Dorsal interior. 



Ozarkian ? (upper Chepultepec), ^ mile S. W. of 

 Elliottsville church, Bess quad., Alabama. Wax re- 

 plicas of originals in Ulrich Coll., U. S. Nat. Mus. 

 Cat. No. S 1582. X 2.65. 



Figs. Syntrophioides harlanensis (Walcott) 

 20. — Ventral interior, with pseudospondylium and diver- 

 gent pallial markings. 

 23. — Dorsal interior, with adductor impressions and an- 

 terior pallial markings. 

 Up. Cambrian, 4 miles N. E. of Rogersville, Tenn. 

 Replicas of Walcott's types (Cat. No. 52252, U. S. 

 Nat. Mus.). Cat. No. S 1583. x 2. 



Clarkella sp. 



6, 11. — Ventral interiors, showing spondylium. 



7, 1 0. — Dorsal interiors, showing numerous septa support- 



ing brachiophore plates. These are not continuous 

 across the middle of the valve but separate as in 

 Syntrophina. 



Ozarkian? , Phillipsburg, Quebec. Cat. No. S 1 567. 



x3. 



Clarkella afif. C. montanensis (Walcott) 



8, 9. — Ventral and dorsal exteriors, showing smooth surface. 

 Ozarkian? (Logan's Bj), near Phillipsburg, Quebec. 

 Geol. Surv. Canada, x 2. 



Multicostella platys (Billings) 



12. — Lenticular profile. 



Ordovician (Chazy), Speer's Ferry, Va. Cat. No. 

 S792. x2. 



HuenelHna triplicata (Walcott) 



14, 21. — Ventral and dorsal internal molds. Ventral inte- 

 rior shows an impression of the pseudospondylium and 

 radiating ridges diverging from it and a strong ante- 

 rior adductor (?) impression. Fig. 21 shows molds 

 of peculiar lateral plates upon which the genus is 

 based. Original in U. S. Nat. Mus. 

 22. — Replica of fig. 21, to show lateral plates. 



Ozarkian?, Novaya Zemlya, Russia. Cat. No. 

 S1580. x2.65. 



Yangtzeella poloi (Martelli) 



24, 25. — Ventral and posterior views of exterior. 



Up. Ordovician, Foope, China. Cat. No. S 1585. 



X 1.33. 

 26. — Dorsal exterior. 



Ordovician (Neichiashan), Neichiashan, Yangtze 



gorge, Hupeh, China. Cat. No. S 1586. x 1.30. 



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