60 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I39 



valve; anterior commissure rectimarginate to ligate to slightly uni- 

 plicate ; surface marked by concentric lines of growth and fine obscure 

 radial costellae ; beak of the pedicle valve short, suberect ; foramen 

 incomplete, large, hypothyrid ; deltidial plates small, disjunct. 



Pedicle valve interior with well-developed but incomplete pedicle 

 collar and thick teeth supported by small, somewhat receding dental 

 plates ; muscle field small, rounded, with small diductor scars sur- 

 rounding large adductor scars. Vascula media prominent, originating 

 between diductor and adjustor scars, extending anteriorly to branch 

 about one-third the length from the front margin. 



Brachial valve interior with corrugated sockets and overhanging 

 socket ridge to which the short, bladelike, spinulifer crura are attached 

 by small and narrow outer hinge plates. Inner hinge plates small and 

 narrow. Median ridge low, thick, extending to the apex. Adductor 

 field small, divided by a low median ridge; anterior adductors rounded, 

 posterior pair elongated. Vascula media widely divergent. 



Type species (by original designation). — Rhynchonella cornea 

 Fischer, in Davidson, Trans. Linnaean Soc, ser. 2, vol. 4, Zool., pt. 2, 

 p. 171, pi. 25, figs. 2-4, 1887. 



Comparisons. — This is one of several triangular or nearly trian- 

 gular genera with faint radial ornamentation. It differs from Frieleia 

 and Compsothyris in not having a strongly camerate apex in the 

 brachial valve of the adult. It differs from Grammetaria in its less 

 prominent radial markings, nonalate deltidial plates, and the develop- 

 ment of the cardinalia which are camerate in the young of Gram- 

 metaria. Aetheia can be readily distinguished from Hispanirhynchia 

 by its small foramen, concave deltidial plates and the great develop- 

 ment of inner hinge plates on the interior. 



Distribution. — In modern seas Hispanirhynchia is known from off 

 the coasts of Morocco, the Sudan, and the Canary Islands. It is also 

 known from west of Cape Finistere, northwestern Spain. It is gener- 

 ally found in deep water, from 577^ fathoms 2 off Cape St. Vincent, 

 Portugal, to below 1,000 fathoms off the coast of Spain. One species, 

 H. fcraneana (Dall) doubtfully assigned, taken off Cocos Island, 

 Panama, came from 117 fathoms. 



Geological horizon. — Possibly present in the Eocene of Cuba. 



Assigned species. — Two Recent species are assigned to this genus : 



Rhynchonella cornea Fischer, Recent, North Atlantic. 

 ? Hemithyris craneana Dall, off Panama, Pacific Ocean. 

 Hispanirhynchia sp., Eocene, Cuba. 



2 See note by Jackson (1918, p. 192, footnote). 



