of Terebratulina septcntrionalis. 417 



six short and stout cirri, all of tlicm curving towards the 

 mouth, which occuj)icd the centre of the base from wliich tlie 

 cirri sprang. 'J'lie digestive sac liung from the moutli, and 

 was twice as kjng as broad, liaving a strong constriction in 

 the centre, forming two cliambers, the lowermost one b(;ing 

 globular in shape and having its walls coloured a light reddish 

 brown, this coloured portion evidently indicating hepatic cells. 

 The cavity next the mouth indicates the stomach, while the 

 lowermost cavity indicates the future intestine or cul-de-sac. 

 The cirri moved fref{uently and in various directions, though 

 generally ))erforming a grasping motion, as if securing some 

 bit of food, imitating precisely the movement of tlie cirri in 

 Polyzoa ; and this resemblance was more conn)lete from the 

 fact that the tentacles were densely clothed with cilia (fig. 4), 

 and their movements caused visible currents in the water. 

 The two cavities of the digestive sac were also ciliated ; and 

 little pellets of food were seen rapidly circulating back and 

 forth from one cavity to the other. The cavities were alter- 

 nately dilating and contracting. At this stage the lower ca- 

 vity of the digestive sac was diverted to the larger valve, as 

 represented in fig. 4. 



In this stage, and several succeeding stages, the outline of 

 the shall is remarkably like that of Linrjula] and this resem- 

 blance is more striking from the proportionally long peduncle. 



In another stage, numerous irregular-shaped calcarcfjus 

 spicula lined the outer margin of tlie ciiTi, while the future 

 position of the calcareous loop, or crura, was indicated by a 

 row of irregvilar-shaped spicula. 



Fig. 8 represents portions of two ciiTi highly magnified, 

 in which coiTCct outlines are given of the spicula. It is 

 by the presence of tlifv^e calcareous particles that we must ac- 

 count for a certain rigidity noticed in the texture of the cirri. 

 In these slightly advanced stages the peduncle becomes much 

 shorter in proportion to the length of the shell, though the 

 shell presents the same Lingula-Wkc form, differing, however, 

 from Lingula in the much greater length of the neural valve, 

 which is always perforated and rostrated from the outset. 



In all these stages the peduncle has very slight adhesion to 

 the rock or whatever substance it may be attached to, in this 

 respect differing greatly from the adult, which often requires 

 great force to detach it, frequently leaving the peduncle sepa- 

 rated from the body and adhering to the rock. 



In side views of the shell at this period (see fig. 5) the 

 flatness of the valves will be observed, again resembling 

 Lingula in this respect ; the under valve is much flatter than 



