12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 149 



this genus the species A. pirguensis, which lacks the exaggerated 

 elevation of the border of the brachial diaphragm (or lophophore plat- 

 form) and possesses a somewhat different aspect of the median 

 septum at its confluence with the cardinal process as compared with 

 the type species, A. grayae (Davidson). He has also included Rafi- 

 nesquina carinata Holtedahl (1916, p. 25, pi. 2, figs. 4-5), the interior 

 of which has never been described or illustrated. Williams (written 

 communication, Jan. 13, 1964) has accepted the generic assignment 

 of A. pirguensis, which we question here, but he joins in questioning 

 that of R. carinata. 



Anoptambonites cf. A. grayae (Davidson) 

 Plate 2, figures 1, 3, 5, 7, 9 



Leptaena grayae Davidson. Davidson, 1883, Mon. Brit. Fossil Brachiopoda, 



vol. 5, pt. 2, Silurian Supplement, p. 171, pi. 12, figs. 23-25. 

 Leptaena llandeiloensis Davidson. Davidson, 1883, Mon. Brit. Fossil Brachiopoda, 



vol. 5, pt. 2, Silurian Supplement, pp. 171-172, pi. 12, fig. 27. 

 Leptella grayae (Davidson). Reed, 1917, Trans. Roy. Soc. Edinburgh, vol. 51, 



pt. 4, No. 26, p. 873, pi. 13, figs. 10-13, 15-17. 

 Leptelloidca grayae (Davidson). Jones, 1928, Mem. Geol. Survey Great Britain, 



Paleontology, vol. 1, pt. 5, pp. 489-490. 

 Anoptambonites grayae (Davidson). Williams, A., 1962, Geol. Soc. London 



Mem. No. 3, p. 171, p. 16, figs. 11, 12, 13, 14, 17. 



Description. — Valves very gently concavo-convex with finely cos- 

 tellate exteriors; costellae increase by implantation and are of a 

 uniform size; interspaces are narrower than costellae, which number 

 10 in 5 mm at the front edge of a shell 13 mm long; greatest con- 

 cavity of the brachial valve is along the midline, producing a sulcate 

 appearance ; the posterolateral flanks are flat or very slightly convex ; 

 pedicle valve obtusely carinate along the midline and gently convex 

 on the flanks. Pedicle interior with small muscle field as in Leptellina; 

 delthyrial cavity with tiny plate close to the apex ; pallial trunks 

 originate near the front of each diductor muscle scar, one pair runs 

 forward parallel to the midline of the valve, bifurcating in about 

 2 mm, the other runs anterolateral^ for about the same distance before 

 bifurcation. Brachial interior with strong median septum terminating 

 against the strongly developed, nearly vertical edge of the visceral 

 disk ; cardinal process, located on a raised quadrate platform between 

 the brachiophores, consists of a pair of exceedingly small linear 

 ridges, chilidial plate covers posterior end ; brachiophores slender rods 

 as in typical Leptellina; pallial markings strongly incised; two pairs 



