426 On the Early Stages q^ Terebratulina septentrionalis. 



reou3 spicula ; en, notch for pallial caeca ; h, hsemal valve ; n, neural 

 valve. 



Plate XV. 



Fig. 1. A few eggs in their natural position, from the pallial membrane 



of an adult individual. 

 Fig. 2, Earliest stage noticed. This was attached to rock, resting upon 



the broad hinge-mai'gin. 

 Fig. 3. Another stage, in which the body has rapidly lengthened, and 



the peduncle is equal in length to the remaining portion of the 



animal. 

 Fig. 4. Stage in which a few cirri are developed, with the oesophagus 



and stomach hanging below. 

 Fig, 5. The animal at rest and in action. 

 Fig. 6. The same, from above, reversed. 

 Fig. 7. A more advanced state, with the liver as a simple hepatic fold on 



each side of the stomach. 

 Fig. 8. Portions of two cirri, highly magnified, to show more plainly the 



form of the spicula. 

 Fig. 9. A portion of the haemal valve. 

 Fig. 10. A portion of the neural valve. 

 Fig. 11. The same portions before separation. 



Fig. 12. A slightly more advanced stage, showing the crown of cirri. 

 Fig. 13. A still more advanced stage, with the haemal valve forcibly 



thrown open, showing the divaricator muscles with the stomach 



between them. The crown of cirri shows the first indications 



of its bilobed character. 

 Fig. 14. A stage more advanced ; valves forcibly opened, showing all the 



parts plainly. 

 Fig. 14 a. A highly magnified view of the stomach, hepatic folds, lateral 



bands, &c. of fig. 14. This figure shows a faecal mass rolled in 



a spiral form, in the act of being discharged through the mouth. 



The line bordering the upper portion of the figure indicates the 



inferior margin of the crural processes. 

 Fig. 15. The haemal valve, with the crown of cirri &c. 

 Fig. 16. A view of fig. 13 with the valves closed. 



Plate XVI. 



Fig. 17. A stage considerably more advanced than the preceding ones, 



showing the lophophore already bilobed, but with the cini not 



deflected. Caecal lobes of the liver few, but separated. 

 Fig, 18. Showing the lophophore with the cirri deflected. 

 Fig, 19. The arms of the lophophore more sharply bent; the central 



processes first indicated. The highly flexible lip is here seen in 



folds. 

 Fig. 20. A stage slightly more advanced than the preceding. The lip is 



seen thrown back, disclosing the capacious mouth. 

 Fig. 21. A stage more advanced, in which the lophophore begins to 



assume the characters of the adult. The cirri are now more 



numerous and more attenuated, and the lip is not so widely 



reflected. 

 Fig. 22. View of the mouth of an adidt individual, showing the oral 



tubercle and oral groove. 

 Fig. 23. Fragment of shell, highly magnified, showing scales, tubules, 



and outer la3'er, with lines of accretion indicated by rows of 



flattened bead-like nodules. 



