LIVING BRACHIOPODA. 347 



Glottidia this nerve arises from the infra-oesophageal gangHa, runs outside of the anterior 

 occhisor muscles, and then follows along on the inside surfaces of the oblique muscles. 

 Hancock represents this nerve as entering and passing through the various muscles it 

 encounters, whereas, in the three species of the family I have studied, the nerve simply 

 passes over the surface of the muscle to which it adheres by sending out little twigs, 

 which penetrate the muscle. At 51: 19 is represented the appearance of these twigs 

 branching from the main nerve. The infra-oesophageal ganglia arise just behind the 

 brachial sinus and Ijelow the oesophagus, and the nerve passes around the anterior and 

 lateral face of the anterior occhisor muscles. The flexures of this nerve, as shown in 

 51: 14, are probably due to the contraction of the parts. 



In Liiujula lepldula the oblique nerves, one on each side of the coelomic cavity, 

 follow in the same path and cling to the oblique muscle in the same way. Blochmann 

 and others represent their appearance correctly. A pair of auditory vesicles is found 

 a short distance back of the dorsal attachment of the anterior occlusor muscles and in 

 close proximity to the inner corner of the opening of the large pallial sinus (47 : 5, 6 ; 

 48 : 5, <) ; 51 : 17, 18 ; 52 : 1, "i ; 53 : 8, 9) . In living L. lep'uhda these otocysts are very clearly 

 defined. As the otocysts are near the dorsal surface, the separate nerves supplying them 

 may be easily made out. These nerves originate from the infra-oesophageal ganglia. 

 The otocyst is a clear, round vesicle, in one drawing (51: 18) appearing perfectly circular 

 and containing a number of otoliths. In one otocyst twenty-five were counted. These 

 are in constant \dbration and these \'ibrations continue long after the parts are mutilated 

 by dissection. The region in which the otocysts are found is a center of great activity. 

 A number of muscles are found here, not only the termination of the great occlusors, but 

 the gastro-parietal muscles and certain muscles that seem to control the great opening of 

 the pallial sinus. 



In Glottidia pymmidata the otocysts were not observed, though I am sure that, as 

 the region in which they occur is now known, they wdll certainly be seen through the 

 partially translucent shell. Professor Brooks discovered their presence in the extreme 

 young of this species in 1878. 



In alcoholic LimjuUdae these vesicles have not been detected, though in life, when 

 the shell is sufficiently transparent, they are easily seen. Even in Lingvla cmatina, where 

 the shell is unusually opaque by the deposition of limy layer's, I managed to find a small 

 specimen in wdiich the shell was sufficiently thin to make out, with great distinctness, 

 these organs (51 : 20) . They were found in precisely the same position as described 

 above in L. lepiduJa. 



In Hancock's classical memoir, plate 61, figure 6, the dorsal aspect of the root of the 

 oesophagus of Macjellania aiistralis is figured. On each side of this region and in close 



