1839.] Linnean Society. 31 



most anteriorly, the common opening of the peritoneal canals ; se- 

 condly, the anus ; thirdly, the Allantoid bladder ; fourthly, the ovi- 

 ducts, with the ureters, which open into the back part of the ovi- 

 ducts. 



The brain consists of two elongated subcompressed distinct cere- 

 bral hemispheres ; a single elliptical optic lobe, or representative of 

 the bigeminal bodies ; a simple transverse cerebellar fold, not cover- 

 ing the widely- open fourth ventricle ; largely developed pineal and 

 pituitary glands ; and a single corpus mammillare. 



The nerves given off from the brain, were the olfactory ; the optic, 

 which arose from the same point at the middle line between the 

 crura cerebri, and did not decussate ; the fifth pair ; the acoustic ; the 

 pneumogastric ; and lingual nerves : there were no traces of the third, 

 fourth, or sixth nerves ; there being no muscles to the eyeballs. 



The eyes are very small, and adhere to the skin, Avhich passes over 

 them without forming any projection ; they have a small spherical 

 lens, and no choroid gland. 



The organ of hearing consists of a vestibule enclosed in a thick 

 cartilaginous case, without external communication except for the 

 foramina transmitting the poriio mollis : it consists of two large 

 otolithic sacs, containing each a white chalky mass ; the external one 

 being six times the size of the one next the brain : above these sacs 

 are three small semicircular canals. No trace of tympanic cavity or 

 Eustachian tube. 



The organ of smell consists of two oval membranous sacs, pli- 

 cated internally, and having each a single external aperture upon 

 the upper lip ; but without any communication with the mouth, — a 

 structure which the author observed was perhaps the only single 

 character which unexceptionably proved the Lepidosiren to be a true 

 fish. The remaining evidence of its ichthyic nature reposed rather 

 upon the concurrence of many less decisive characters. 



These characters were stated to be, its covering of large round 

 scales ; the mucous ducts of the head and lateral line ; the many- 

 jointed soft ray supporting the rudimental pectoral and ventral fins ; 

 the gelatinous vertebral chord, united anteriorly to the whole of the 

 basi- occipital, and not to two condyles as in Batrachia ; a prae- 

 opercular bone, the intermaxillary bone being moveable ; the lower 

 jaw having each ramus composed simply of a post-mandibular and 

 dentary piece ; the double row of spinous processes, both above and 

 below the vertebral chord ; the green colour of the ossified parts of 

 the skeleton ; the straight intestine, with its spiral valve ; the absence 

 of pancreas and spleen ; the single peritoneal outlet ; the position 



