454 Transactions. 



riiu : if so, they should be termed pseudotela, and the foramen would be 

 pseudotelate. Further investigation of this matter is required, and perhaps 

 may best be undertaken by those who have the opportunity to obtain 

 and study fresh Recent specimens. With such material at hand notice 

 might be taken of the part played by the pedicle in depositing test in the 

 foramen. In the inside of the labium :)f fossil Terebratulids with labiate 

 foramen may be found a tongue-shaped layer of test which one supposes 

 to have been deposited by the pedicle : if so, this should merit distinction 

 as the pedicle- plate, to be looked for in connection with a remigrant 

 foramen. Then the question comes whether similar secretion by the 

 pedicle has played any part in the fusing of the deltidial plates. To the 

 fused deltidial plates as shown by Terebratulids I have given, in the 

 memoir already mentioned, the name of symphytimn, from the likeness to 

 the closing-up of a wound. In some well-preserved epithyrid Terebratulids 

 the middle area of the symphytium seems to be distinct, with very con- 

 siderable resemblance to the pedicle-plate. And in some shells the 

 sym|)hytium seems to be composed entirely of this middle piece. Now, 

 there arises the suspicion that this middle piece has been laid down at 

 first in between, and later on the foraminal edge of, the coalescing 

 deltidial plates. For if there was simple coalescence of the deltidial plates, 

 growing together from the edges of the delthyrium, as they certainly 

 do in liypothyrid Rhynchonellids with concrete deltidial plates, then the 

 lines of growth should run longitudinally, more or less parallel with the 

 diverging edges of the delthyrium. But in the piece under consideration 

 the lines of growth appear as transverse rugosities — the transverse direction 

 being what would be expected from deposition by the pedicle, and the 

 rugosities being connected with the swelling and attenuation of the pedicle 

 under muscular stimulus — connected possibly with periodical variations of 

 marine conditions. 



Now, if such arguments be correct, the symphytium — the final closing 

 of the deltidial plates — in epithyrid shells is to be distinguished altogether 

 from the conjunct or concrete deltidial plates of hypothyrid shells. One 

 should find, perhaps, in mesothyrid shells concrete deltidial jilates united 

 near the cardinal margin, but separated medianly (that is, the part nearer 

 the apex), and, lying in this separation, the beginning of the symphytium 

 with its transverse rugosities ; and in epithyrid shells, a later develop- 

 ment, perhaps only the symphytium, margined possibly by a relic of the 

 deltidial plates. 



To observe these details in fossil shells means much excavation, with 

 results not always satisfactory, on account of defective preservation. One 

 may hope that those who have the opportunity to examine Recent 

 epithyrid shells may be abh' to supply further details. 



