23 



but its anterior extremity is embraced by a pair of retractor muscles, which arise 

 from the posterior margins of the lower mandible. The fleshy substance of 

 the tongue, thus supported, is produced anteriorly, and forms three caruncles 

 (c. fig. 7. pi. 8.) very soft in texture, and beset by numerous papillce, having all 

 the characters of a perfect organ of taste. The anterior or terminal caruncle is 

 the largest, and four delicate retractor or depressor muscles are inserted into it. 

 These arise, two on either side, below the os hyoides, from the membrane closing 

 the lower part of the mouth. 



Behind the caruncles the dorsum of the tongue is encased with a thin layer of 

 horny matter about five lines in length, from which arise four longitudinal rows 

 of slender recurved prickles {b. fig. 7. pi. 8.), between one and two lines in length. 

 The number of these prickles is precisely that of the labial tentacles, there being 

 twelve in each row. An analogous structure obtains in the Cephalopoda and in 

 many of the Gasteropoda. The necessity of such a structure becomes very 

 apparent in the Pearly Nautilus, if, as Rumphius has asserted, it creeps with 

 the shell uppermost ; since, in that case, the tongue, having its position re- 

 versed, would be opposed, instead of being assisted by gravitation while regu- 

 lating the movements of the food in the mouth. And it is worthy of remark, 

 that in the Flamingo, which turns the upper mandible to the ground while taking 

 its food, the tongue is similarly armed with singularly developed recurved spines, 

 calculated, as in the Pearly Nautilus, to rake the alimentary morsels towards the 

 fauces. Behind the horny part, the tongue again becomes soft and papillose, 

 but the papillae are coarser and larger than those on the anterior caruncles. 

 At the back of the mouth two broad fleshy processes project forwards from the 

 sides of the fauces ; these also are papillose, and are perforated in the middle 

 of their inner surfaces by a small aperture which leads into a glandular cavity, 

 situated between the folds of the membrane. An opake whitish substance could 

 be expressed from these cavities, which were the only traces of a salivary system 

 detected in this animal ; although, from the remarkable development of these 

 glands in the Dibranchiate Cephalopods, they were naturally expected and care- 

 fully sought for in the Pearly Nautilus. 



The pharynx has numerous longitucUnal rugae internally, and is evidently 

 capable of considerable dilatation. The oesophagus {s. pi. 4.) is three fourths of 

 an inch in length, and after having passed beneath the brain, or commissure of 



