NO. 5 RHYNCHONELLOID BRACHIOPODS — COOPER 27 



Another specimen, possibly the same species, is from 153 fathoms. 

 Basiliola lucida is from waters of 56 fathoms down to 122 fathoms 

 and the temperature range is from 51 ° F. to 63 ° F. 



Assigned species. — The following species are assigned to Basiliola: 



Hemithyris beech eri Dall, Recent, Hawaiian Islands. 

 Basiliola pompholyx Dall, Recent, Philippines. 

 Rhynchonella lucida Gould, Recent, Japan. 

 Basiliola nitida Cooper, Pliocene, Okinawa. 

 B. elongata Cooper, new species, Recent, Philippines. 



Discussion. — Basiliola with its strongly unequal valves and small 

 foramen bounded by auriculate deltidial plates is usually easy to recog- 

 nize. The shells range from hyalescent when living to opaque in the 

 older or dead shells. The color ranges from pale yellow-brown to 

 brownish gray. The anterior commissure is usually strongly folded 

 in the dorsal direction, a long tongue from the pedicle valve fitting into 

 the deeply reentrant brachial valve. Although the anterior uniplica- 

 tion is strong, the fold on the brachial valve is not, as a rule, well 

 defined. Except for the uniplicate commissure the valves are not 

 otherwise plicated, nor do they have any radial markings. 



Aside from the smooth shell and uniplication the only other distinc- 

 tive exterior feature of Basiliola is the beak. This is generally not 

 much elongated but is bluntly pointed. The foramen is usually small 

 circular, longitudinally oval, or elongated elliptical. The anterior side 

 of the foramen is usually bounded in all the species by a moderate 

 to elaborate flange or auriculation. In B. beecheri and lucida this is 

 present but not as exceptionally developed as in B. pompholyx. 



The deltidial plates are conjunct and often so tightly joined as to 

 approximate a symphytium. The anterior margin of the deltidial 

 plates commonly rests on the umbo of the brachial valve. In old 

 shells the movement of the umbo against the anterior margin of the 

 deltidial plates leaves a smooth area. In some specimens an extension 

 grows anteriorly from the anterior margin of the deltidial plates along 

 the surface of the umbonal slope of the brachial valve. This usually 

 is part of the pedicle collar. 



The chief character on which Dall based his genus is the pedicle 

 collar and which is elaborate in many specimens. It is best seen in 

 B. pompholyx (pi. 12, fig. 10) although it is well developed in the 

 other species. The collar is built as a plate from the anterior edge of 

 the deltidial plates as mentioned above and extends around the inside 

 of the apex. The collar in many specimens is clear of the valve floor 

 but in others shell substance has been added under the free antero- 

 ventral edge. 



