200 INTESTINAL STRUCTURE OF FOSSIL FISHES, 
of fishes, or the contents of their intestines, still 
retaining the form of the tortuous tube in which 
they were lodged. To these remarkable fossils 
he has given the name of ColoUtes. (PI. 15' is 
copied from one of a series that are engraved in 
Goldfuss. Petrefacten, PI. Q6.) He has also 
found similar tortuous petrifactions within the 
abdominal cavity of fossil fishes, belonging to 
several species of the genus Thrissops and Lep^ 
tolepis, occupying the ordinary position of the 
intestines between the ribs.* (See Agassiz Pois- 
sons Fossiles, liv. 2, Appendix, p. 15.) 
* As these Cololites are most frequently found insulated in 
the lithographic limestone, M. Agassiz has ingeniously explained 
this fact by observing the process of decomposition of dead 
fishes in the lakes of Switzerland. The dead fish floats on 
the surface, with its belly upwards, until the abdomen is so 
distended with putrid gas, that it bursts : through the aperture 
thus formed the bowels come forth into the water, still adhering 
together in their natural state of convolution. This intestinal 
mass is soon torn from the body by the movement of the waves ; 
the fish then sinks, and the bowels continue a long time floating 
on the water : if cast on shore, they remain many days upon the 
sand before they are completely decomposed. The small bowels 
only are thus detached from the body, the stomach and other 
viscera remain within it. 
We owe this illustration of the nature of these fossil bodies, 
whose origin has hitherto been inexplicable, to the author of a 
most important work on fossil fishes, now under publication 
at Neuchatel. His qualifications for so great and difiicult a 
task are abundantly guaranteed by the fact, that Cuvier, oh 
seeing the progress he had made, at once placed at the disposal 
of Professor Agassiz the materials he had himself collected 
towards a similar work. 
