386 Scientific Notices^^Zoologt/. [Nov. 



two-thirds of the number rose above the surface of the water. 

 It was then expanded to the uttermost, and thiown baqk upon 

 the water, hke the foot of a lymneoua when commeneing to 

 swim; in the next place it was coatracted at the jedge, and 

 formed into the shapj^ of a hood, enclosing a g;lob'ule-of air, 

 ivhioh w*& alowly applied to the extiremity ot the iloaU A. vibva- 

 tory movement could now be perceived throughout: the foot, 

 and when it was thrown back again to renew the process, the 

 globule was found inclosed in its newly constructed envelope. 



It doe^not appear that the janthinse ever ,Ein|L,,^e)ip\Y, ihe 

 surface, while they remain attached to the vesicle ; bi^t, ;iynen 

 they aJj^ .entirely separated, they immediately fall to tl^isqottom 

 of the tumbler, and are unable afterwards to rise fi;Q^ft their 

 position, and though they continue to be vigorous for some time, 

 they generally die in a lew days. As their respiratory organs 

 are calculated for the, water, this circumstance is probably acci- 

 dental*M;i o'Aj^'\ w. .- ;■.,•■ . -jLv -i'^u *i- < '■ 



Along tthfcS surface, of the float passes a httle IJDei off pearly 

 fibres, and upon this line are attached the egg of the animal. In 

 J. fragilis tiie float is convex> slightly scaled above, and concave 

 beneathi strait and composed of large vesicles. In the I. globosa 

 it is composed of smaller, it is flat above and beneath, and by 

 the re-union of one of the edges, it is formed into a spiral and 

 Hearly circular disk. \ \\]\\n \\ ■^■^■^^ 



. Thjei float appears toi Wii50TW»t?Vcted for the purpose of sup- 

 portiog lits isheli and its young upon the surface of the water, 

 and is.secreted.by the foot, and has no attachment to the animal 

 except by the close cohesion resulting from the nice adaptatioa 

 of their proximate surfaces. 



8. On the Vertehrcc of Reptiles and AmpJuhia, By R. Harlan. 



Cuvier, in his Ossemens les Fossil,remarks, ** the dorsal vertebra 

 of the Maestricht animal have their transverse apophyses short, 

 and terminated by an articulating surface enlarged vertically, 

 which carries the ribs, which is consequently attached by a 

 single head;- this characterizes the monitors, and most of the 

 Saurians, excepting only the crocodile, in which particular this 

 structure is absent, with the exception of the three last ribs." 



To the Crocodiles, as an exception, Cuvier should have added 

 the Ichthyosaurus, Iguana, and Camelion, amongst the Sau- 

 rians, together with the Crotalus and Coluber amongst the 

 Ophidia, m all which the ribs are articulated with the bodies of 

 ihe vertebrje by two tubercles, but do not unite M^itlk/Ahe trans- 

 verse process as in the Crocodile. t^ ^' ' 



Conceiving it highly important to the science of Osteology, 

 to ascertain correctly the manner in which the ribs of the difler- 

 ent genera of the Saurian Family are articulated ; as far as my 

 examinations have extended (with the exception of those genera 



