NO. 5 RHYNCHONELLOID BRACHIOPODS — COOPER 6l 



Discussion. — External features of importance in this genus are the 

 beak characters, the ornamentation, and the anterior commissure. In 

 the type species the deltidial plates are well developed and disjunct 

 but in some specimens approach each other very closely. Dall de- 

 scribes the deltidial plates of H. fcraneana as "obsolete" but the speci- 

 men has definitely been damaged in the beak region. In some old 

 specimens of H. cornea these plates are also lacking, possibly due to 

 abrasion. 



The shell of young specimens of Hispanirhynchia is generally 

 translucent and a pale brown. Adults are opaque and a deeper brown 

 in color. The surface is minutely costellate, the costellae extremely 

 fine and very closely crowded. 



Specimens of H. cornea are generally rectimarginate but Thomson 

 (1927, p. 159) speaks of some as being ligate, that is, with a gentle 

 depression in each valve which will produce an emarginate anterior. 

 The anterior commissure of H. fcraneana, on the other hand, has a 

 slight wave in it toward the pedicle valve, thus producing a faint 

 sulcation. 



The interior of the pedicle valve of the mature to old shells usually 

 shows the details to perfection because the muscles and pallial marks 

 are deeply impressed. The pedicle collar is well developed and may be 

 elevated above the valve floor. The teeth are strong and corrugated. 

 The dental plates are strong and separated from the lateral shell wall 

 by deep cavities. In old shells these tend to become nearly obliterated 

 by deposition of shell substance inside the cavities. 



The muscle field is small. The flabellate diductor scars are small 

 and surround a fairly large adductor patch anteriorly. The adjust- 

 tor scars are deeply impressed at the anterior edge of the dental 

 plates. Accessory diductor scars are not visible in the delthyrial cavity. 

 The vascula media take off anterior to the adjustor scars and along the 

 outside of the diductor scars. The main trunk branches at about mid- 

 valve, one branch extending laterally, the other anteromedially. Both 

 of these branches bifurcate again to produce distributaries anteriorly 

 and laterally. 



The genital area is small and located on the shell wall just anterior 

 to the dental plates. This area is smaller than that in Basiliola and 

 Rhytirhynchia. 



The cardinalia of this genus are interesting because the young show 

 features that are buried by excess shell in the adult. The insertion of 

 the diductor muscles appears as a small, triangular, horizontally stri- 

 ated pit at the apex. No swollen cardinal process is present as in 



