716 DEEP WATER MOLLUSKS AND BE ACE lOPOufi—lj. ILL. vol.xvii. 



wLich liad closed their valves on the tips of the brachia, confirming 

 the observations of Morse that these organs may be protruded beyond 

 the valves. Fischer reports the same fact with regard to Hemitliyris 

 cornea^ dredged off the African coast by the Talisman. 



The differences which separate this group from Hemitliyris are suffi- 

 ciently obvious, though perhaps they would have been regarded for- 

 merly as of not more than subgeneric rank. When the closeness with 

 which the lines have been drawn among the fossil genera are consid- 

 ered, the relative rank of this one seems fully generic. The nearest 

 relative of ^r/e?eia among fossil RliynchonclUdce is probably to be found 

 in the genera CamaroUechia and Leiorhynchus, Hall, a plicated group 

 of forms which flourished in the middle and later Devonian and early 

 Carboniferous j)6riods. In the former the crural laminae, separate in 

 the young state, are united by the deposit of callus on a cup like expan- 

 sion of the medial septum in the old individuals. In the very young 

 Frieleia the crura lie on the summit of an arch of which one limb joins 

 the side of the valve and the other unites with the keel of the septum, 

 leaving a triangular surface of which the apex is on the septum, the 

 base formed by the cardinal margin and the sides by the inner limbs 

 of the two arches. As the shell grows this condition is modified, so 

 that the anterior edge of the incipient spondylium is free from the sep- 

 tum and overhangs it. In well developed full-grown specimens the 

 suture of the spondylium is entirely coalescent and the separation 

 indicated only by the notch in the front edge and the groove on the 

 upper surface. In young or imperfectly developed adolescent speci- 

 mens the notch may be, and frequently is, deeper; but in none, young 

 or old, does the connection with the septum fail or is the suture fully 

 open to the cardinal border. The thickening due to age sometimes 

 almost develops a cardinal process on the apex of the brachial valve. 

 As in all articulate brachiopods, the comparative elongation and infla- 

 tion, or widening and compression, varies with different individuals. 

 One specimen has the peduncular foramen completely closed in the 

 median line below. Another, owing to some accident in youth, has a 

 deep mesial groove in both valves from about the middle of the shell, 

 giving the specimen almost the look of a Bilobites. Another has 

 repaired the damage done by an extensive fracture with a sheet of 

 shell substance, which shows that the secretion of shelly matter is not 

 confined to peripheral parts of the mantle. The prismatic structure of 

 the new shell deposit is similar in all respects to that of the old. Many 

 of the shells are bored by an agency which produces results like the 

 borings of Gliona. The shells are very free from sessile organisms, 

 only a few Polyzoa or arenaceous foramiiiifera being observed. A few 

 dead valves were noticed which seemed to have been pierced in the 

 visceral region by some carnivorous gastropod, a misfortune from which 

 brachiopods as a rule are remarkably free. 



